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121 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Axel Rasmussen
|
f619147104 |
userfaultfd: add UFFDIO_CONTINUE ioctl
This ioctl is how userspace ought to resolve "minor" userfaults. The
idea is, userspace is notified that a minor fault has occurred. It
might change the contents of the page using its second non-UFFD mapping,
or not. Then, it calls UFFDIO_CONTINUE to tell the kernel "I have
ensured the page contents are correct, carry on setting up the mapping".
Note that it doesn't make much sense to use UFFDIO_{COPY,ZEROPAGE} for
MINOR registered VMAs. ZEROPAGE maps the VMA to the zero page; but in
the minor fault case, we already have some pre-existing underlying page.
Likewise, UFFDIO_COPY isn't useful if we have a second non-UFFD mapping.
We'd just use memcpy() or similar instead.
It turns out hugetlb_mcopy_atomic_pte() already does very close to what
we want, if an existing page is provided via `struct page **pagep`. We
already special-case the behavior a bit for the UFFDIO_ZEROPAGE case, so
just extend that design: add an enum for the three modes of operation,
and make the small adjustments needed for the MCOPY_ATOMIC_CONTINUE
case. (Basically, look up the existing page, and avoid adding the
existing page to the page cache or calling set_page_huge_active() on
it.)
Link: https://lkml.kernel.org/r/20210301222728.176417-5-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
||
|
Axel Rasmussen
|
7677f7fd8b |
userfaultfd: add minor fault registration mode
Patch series "userfaultfd: add minor fault handling", v9. Overview ======== This series adds a new userfaultfd feature, UFFD_FEATURE_MINOR_HUGETLBFS. When enabled (via the UFFDIO_API ioctl), this feature means that any hugetlbfs VMAs registered with UFFDIO_REGISTER_MODE_MISSING will *also* get events for "minor" faults. By "minor" fault, I mean the following situation: Let there exist two mappings (i.e., VMAs) to the same page(s) (shared memory). One of the mappings is registered with userfaultfd (in minor mode), and the other is not. Via the non-UFFD mapping, the underlying pages have already been allocated & filled with some contents. The UFFD mapping has not yet been faulted in; when it is touched for the first time, this results in what I'm calling a "minor" fault. As a concrete example, when working with hugetlbfs, we have huge_pte_none(), but find_lock_page() finds an existing page. We also add a new ioctl to resolve such faults: UFFDIO_CONTINUE. The idea is, userspace resolves the fault by either a) doing nothing if the contents are already correct, or b) updating the underlying contents using the second, non-UFFD mapping (via memcpy/memset or similar, or something fancier like RDMA, or etc...). In either case, userspace issues UFFDIO_CONTINUE to tell the kernel "I have ensured the page contents are correct, carry on setting up the mapping". Use Case ======== Consider the use case of VM live migration (e.g. under QEMU/KVM): 1. While a VM is still running, we copy the contents of its memory to a target machine. The pages are populated on the target by writing to the non-UFFD mapping, using the setup described above. The VM is still running (and therefore its memory is likely changing), so this may be repeated several times, until we decide the target is "up to date enough". 2. We pause the VM on the source, and start executing on the target machine. During this gap, the VM's user(s) will *see* a pause, so it is desirable to minimize this window. 3. Between the last time any page was copied from the source to the target, and when the VM was paused, the contents of that page may have changed - and therefore the copy we have on the target machine is out of date. Although we can keep track of which pages are out of date, for VMs with large amounts of memory, it is "slow" to transfer this information to the target machine. We want to resume execution before such a transfer would complete. 4. So, the guest begins executing on the target machine. The first time it touches its memory (via the UFFD-registered mapping), userspace wants to intercept this fault. Userspace checks whether or not the page is up to date, and if not, copies the updated page from the source machine, via the non-UFFD mapping. Finally, whether a copy was performed or not, userspace issues a UFFDIO_CONTINUE ioctl to tell the kernel "I have ensured the page contents are correct, carry on setting up the mapping". We don't have to do all of the final updates on-demand. The userfaultfd manager can, in the background, also copy over updated pages once it receives the map of which pages are up-to-date or not. Interaction with Existing APIs ============================== Because this is a feature, a registered VMA could potentially receive both missing and minor faults. I spent some time thinking through how the existing API interacts with the new feature: UFFDIO_CONTINUE cannot be used to resolve non-minor faults, as it does not allocate a new page. If UFFDIO_CONTINUE is used on a non-minor fault: - For non-shared memory or shmem, -EINVAL is returned. - For hugetlb, -EFAULT is returned. UFFDIO_COPY and UFFDIO_ZEROPAGE cannot be used to resolve minor faults. Without modifications, the existing codepath assumes a new page needs to be allocated. This is okay, since userspace must have a second non-UFFD-registered mapping anyway, thus there isn't much reason to want to use these in any case (just memcpy or memset or similar). - If UFFDIO_COPY is used on a minor fault, -EEXIST is returned. - If UFFDIO_ZEROPAGE is used on a minor fault, -EEXIST is returned (or -EINVAL in the case of hugetlb, as UFFDIO_ZEROPAGE is unsupported in any case). - UFFDIO_WRITEPROTECT simply doesn't work with shared memory, and returns -ENOENT in that case (regardless of the kind of fault). Future Work =========== This series only supports hugetlbfs. I have a second series in flight to support shmem as well, extending the functionality. This series is more mature than the shmem support at this point, and the functionality works fully on hugetlbfs, so this series can be merged first and then shmem support will follow. This patch (of 6): This feature allows userspace to intercept "minor" faults. By "minor" faults, I mean the following situation: Let there exist two mappings (i.e., VMAs) to the same page(s). One of the mappings is registered with userfaultfd (in minor mode), and the other is not. Via the non-UFFD mapping, the underlying pages have already been allocated & filled with some contents. The UFFD mapping has not yet been faulted in; when it is touched for the first time, this results in what I'm calling a "minor" fault. As a concrete example, when working with hugetlbfs, we have huge_pte_none(), but find_lock_page() finds an existing page. This commit adds the new registration mode, and sets the relevant flag on the VMAs being registered. In the hugetlb fault path, if we find that we have huge_pte_none(), but find_lock_page() does indeed find an existing page, then we have a "minor" fault, and if the VMA has the userfaultfd registration flag, we call into userfaultfd to handle it. This is implemented as a new registration mode, instead of an API feature. This is because the alternative implementation has significant drawbacks [1]. However, doing it this was requires we allocate a VM_* flag for the new registration mode. On 32-bit systems, there are no unused bits, so this feature is only supported on architectures with CONFIG_ARCH_USES_HIGH_VMA_FLAGS. When attempting to register a VMA in MINOR mode on 32-bit architectures, we return -EINVAL. [1] https://lore.kernel.org/patchwork/patch/1380226/ [peterx@redhat.com: fix minor fault page leak] Link: https://lkml.kernel.org/r/20210322175132.36659-1-peterx@redhat.com Link: https://lkml.kernel.org/r/20210301222728.176417-1-axelrasmussen@google.com Link: https://lkml.kernel.org/r/20210301222728.176417-2-axelrasmussen@google.com Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michal Koutn" <mkoutny@suse.com> Cc: Michel Lespinasse <walken@google.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Xu <peterx@redhat.com> Cc: Shaohua Li <shli@fb.com> Cc: Shawn Anastasio <shawn@anastas.io> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Steven Price <steven.price@arm.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Adam Ruprecht <ruprecht@google.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Cannon Matthews <cannonmatthews@google.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Oliver Upton <oupton@google.com> Cc: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
|
6dfeaff93b |
hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp
Huge pmd sharing for hugetlbfs is racy with userfaultfd-wp because userfaultfd-wp is always based on pgtable entries, so they cannot be shared. Walk the hugetlb range and unshare all such mappings if there is, right before UFFDIO_REGISTER will succeed and return to userspace. This will pair with want_pmd_share() in hugetlb code so that huge pmd sharing is completely disabled for userfaultfd-wp registered range. Link: https://lkml.kernel.org/r/20210218231206.15524-1-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Peter Xu <peterx@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Adam Ruprecht <ruprecht@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Cannon Matthews <cannonmatthews@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> Cc: David Rientjes <rientjes@google.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michal Koutn" <mkoutny@suse.com> Cc: Michel Lespinasse <walken@google.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Oliver Upton <oupton@google.com> Cc: Shaohua Li <shli@fb.com> Cc: Shawn Anastasio <shawn@anastas.io> Cc: Steven Price <steven.price@arm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Daniel Colascione
|
b537900f15 |
userfaultfd: use secure anon inodes for userfaultfd
This change gives userfaultfd file descriptors a real security context, allowing policy to act on them. Signed-off-by: Daniel Colascione <dancol@google.com> [LG: Remove owner inode from userfaultfd_ctx] [LG: Use anon_inode_getfd_secure() in userfaultfd syscall] [LG: Use inode of file in userfaultfd_read() in resolve_userfault_fork()] Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Paul Moore <paul@paul-moore.com> |
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Lokesh Gidra
|
d0d4730ac2 |
userfaultfd: add user-mode only option to unprivileged_userfaultfd sysctl knob
With this change, when the knob is set to 0, it allows unprivileged users to call userfaultfd, like when it is set to 1, but with the restriction that page faults from only user-mode can be handled. In this mode, an unprivileged user (without SYS_CAP_PTRACE capability) must pass UFFD_USER_MODE_ONLY to userfaultd or the API will fail with EPERM. This enables administrators to reduce the likelihood that an attacker with access to userfaultfd can delay faulting kernel code to widen timing windows for other exploits. The default value of this knob is changed to 0. This is required for correct functioning of pipe mutex. However, this will fail postcopy live migration, which will be unnoticeable to the VM guests. To avoid this, set 'vm.userfault = 1' in /sys/sysctl.conf. The main reason this change is desirable as in the short term is that the Android userland will behave as with the sysctl set to zero. So without this commit, any Linux binary using userfaultfd to manage its memory would behave differently if run within the Android userland. For more details, refer to Andrea's reply [1]. [1] https://lore.kernel.org/lkml/20200904033438.GI9411@redhat.com/ Link: https://lkml.kernel.org/r/20201120030411.2690816-3-lokeshgidra@google.com Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Xu <peterx@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Stephen Smalley <stephen.smalley.work@gmail.com> Cc: Eric Biggers <ebiggers@kernel.org> Cc: Daniel Colascione <dancol@dancol.org> Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Jeff Vander Stoep <jeffv@google.com> Cc: <calin@google.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Shaohua Li <shli@fb.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Nitin Gupta <nigupta@nvidia.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Iurii Zaikin <yzaikin@google.com> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Daniel Colascione <dancol@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Lokesh Gidra
|
37cd0575b8 |
userfaultfd: add UFFD_USER_MODE_ONLY
Patch series "Control over userfaultfd kernel-fault handling", v6. This patch series is split from [1]. The other series enables SELinux support for userfaultfd file descriptors so that its creation and movement can be controlled. It has been demonstrated on various occasions that suspending kernel code execution for an arbitrary amount of time at any access to userspace memory (copy_from_user()/copy_to_user()/...) can be exploited to change the intended behavior of the kernel. For instance, handling page faults in kernel-mode using userfaultfd has been exploited in [2, 3]. Likewise, FUSE, which is similar to userfaultfd in this respect, has been exploited in [4, 5] for similar outcome. This small patch series adds a new flag to userfaultfd(2) that allows callers to give up the ability to handle kernel-mode faults with the resulting UFFD file object. It then adds a 'user-mode only' option to the unprivileged_userfaultfd sysctl knob to require unprivileged callers to use this new flag. The purpose of this new interface is to decrease the chance of an unprivileged userfaultfd user taking advantage of userfaultfd to enhance security vulnerabilities by lengthening the race window in kernel code. [1] https://lore.kernel.org/lkml/20200211225547.235083-1-dancol@google.com/ [2] https://duasynt.com/blog/linux-kernel-heap-spray [3] https://duasynt.com/blog/cve-2016-6187-heap-off-by-one-exploit [4] https://googleprojectzero.blogspot.com/2016/06/exploiting-recursion-in-linux-kernel_20.html [5] https://bugs.chromium.org/p/project-zero/issues/detail?id=808 This patch (of 2): userfaultfd handles page faults from both user and kernel code. Add a new UFFD_USER_MODE_ONLY flag for userfaultfd(2) that makes the resulting userfaultfd object refuse to handle faults from kernel mode, treating these faults as if SIGBUS were always raised, causing the kernel code to fail with EFAULT. A future patch adds a knob allowing administrators to give some processes the ability to create userfaultfd file objects only if they pass UFFD_USER_MODE_ONLY, reducing the likelihood that these processes will exploit userfaultfd's ability to delay kernel page faults to open timing windows for future exploits. Link: https://lkml.kernel.org/r/20201120030411.2690816-1-lokeshgidra@google.com Link: https://lkml.kernel.org/r/20201120030411.2690816-2-lokeshgidra@google.com Signed-off-by: Daniel Colascione <dancol@google.com> Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <calin@google.com> Cc: Daniel Colascione <dancol@dancol.org> Cc: Eric Biggers <ebiggers@kernel.org> Cc: Iurii Zaikin <yzaikin@google.com> Cc: Jeff Vander Stoep <jeffv@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nitin Gupta <nigupta@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Shaohua Li <shli@fb.com> Cc: Stephen Smalley <stephen.smalley.work@gmail.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Jann Horn
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4d45e75a99 |
mm: remove the now-unnecessary mmget_still_valid() hack
The preceding patches have ensured that core dumping properly takes the mmap_lock. Thanks to that, we can now remove mmget_still_valid() and all its users. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Link: http://lkml.kernel.org/r/20200827114932.3572699-8-jannh@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linus Torvalds
|
97d052ea3f |
A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in various
situations caused by the lockdep additions to seqcount to validate that
the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict per
CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored and
write_seqcount_begin() has a lockdep assertion to validate that the
lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API is
unchanged and determines the type at compile time with the help of
_Generic which is possible now that the minimal GCC version has been
moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs which
have been addressed already independent of this.
While generaly useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if the
writers are serialized by an associated lock, which leads to the well
known reader preempts writer livelock. RT prevents this by storing the
associated lock pointer independent of lockdep in the seqcount and
changing the reader side to block on the lock when a reader detects
that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
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Linus Torvalds
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f9bf352224 |
userfaultfd: simplify fault handling
Instead of waiting in a loop for the userfaultfd condition to become true, just wait once and return VM_FAULT_RETRY. We've already dropped the mmap lock, we know we can't really successfully handle the fault at this point and the caller will have to retry anyway. So there's no point in making the wait any more complicated than it needs to be - just schedule away. And once you don't have that complexity with explicit looping, you can also just lose all the 'userfaultfd_signal_pending()' complexity, because once we've set the correct process sleeping state, and don't loop, the act of scheduling itself will be checking if there are any pending signals before going to sleep. We can also drop the VM_FAULT_MAJOR games, since we'll be treating all retried faults as major soon anyway (series to regularize and share more of fault handling across architectures in a separate series by Peter Xu, and in the meantime we won't worry about the possible minor - I'll be here all week, try the veal - accounting difference). Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Ahmed S. Darwish
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2ca97ac8bd |
userfaultfd: Use sequence counter with associated spinlock
A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200720155530.1173732-23-a.darwish@linutronix.de |
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Michel Lespinasse
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c1e8d7c6a7 |
mmap locking API: convert mmap_sem comments
Convert comments that reference mmap_sem to reference mmap_lock instead. [akpm@linux-foundation.org: fix up linux-next leftovers] [akpm@linux-foundation.org: s/lockaphore/lock/, per Vlastimil] [akpm@linux-foundation.org: more linux-next fixups, per Michel] Signed-off-by: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Liam Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ying Han <yinghan@google.com> Link: http://lkml.kernel.org/r/20200520052908.204642-13-walken@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Michel Lespinasse
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3e4e28c5a8 |
mmap locking API: convert mmap_sem API comments
Convert comments that reference old mmap_sem APIs to reference corresponding new mmap locking APIs instead. Signed-off-by: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Liam Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ying Han <yinghan@google.com> Link: http://lkml.kernel.org/r/20200520052908.204642-12-walken@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Michel Lespinasse
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42fc541404 |
mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked()
Add new APIs to assert that mmap_sem is held. Using this instead of rwsem_is_locked and lockdep_assert_held[_write] makes the assertions more tolerant of future changes to the lock type. Signed-off-by: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Liam Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ying Han <yinghan@google.com> Link: http://lkml.kernel.org/r/20200520052908.204642-10-walken@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Michel Lespinasse
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d8ed45c5dc |
mmap locking API: use coccinelle to convert mmap_sem rwsem call sites
This change converts the existing mmap_sem rwsem calls to use the new mmap locking API instead. The change is generated using coccinelle with the following rule: // spatch --sp-file mmap_lock_api.cocci --in-place --include-headers --dir . @@ expression mm; @@ ( -init_rwsem +mmap_init_lock | -down_write +mmap_write_lock | -down_write_killable +mmap_write_lock_killable | -down_write_trylock +mmap_write_trylock | -up_write +mmap_write_unlock | -downgrade_write +mmap_write_downgrade | -down_read +mmap_read_lock | -down_read_killable +mmap_read_lock_killable | -down_read_trylock +mmap_read_trylock | -up_read +mmap_read_unlock ) -(&mm->mmap_sem) +(mm) Signed-off-by: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Liam Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ying Han <yinghan@google.com> Link: http://lkml.kernel.org/r/20200520052908.204642-5-walken@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
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14819305e0 |
userfaultfd: wp: declare _UFFDIO_WRITEPROTECT conditionally
Only declare _UFFDIO_WRITEPROTECT if the user specified UFFDIO_REGISTER_MODE_WP and if all the checks passed. Then when the user registers regions with shmem/hugetlbfs we won't expose the new ioctl to them. Even with complete anonymous memory range, we'll only expose the new WP ioctl bit if the register mode has MODE_WP. Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@fb.com> Link: http://lkml.kernel.org/r/20200220163112.11409-18-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
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23080e2783 |
userfaultfd: wp: don't wake up when doing write protect
It does not make sense to try to wake up any waiting thread when we're write-protecting a memory region. Only wake up when resolving a write protected page fault. Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@fb.com> Link: http://lkml.kernel.org/r/20200220163112.11409-16-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Andrea Arcangeli
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63b2d4174c |
userfaultfd: wp: add the writeprotect API to userfaultfd ioctl
Introduce the new uffd-wp APIs for userspace. Firstly, we'll allow to do UFFDIO_REGISTER with write protection tracking using the new UFFDIO_REGISTER_MODE_WP flag. Note that this flag can co-exist with the existing UFFDIO_REGISTER_MODE_MISSING, in which case the userspace program can not only resolve missing page faults, and at the same time tracking page data changes along the way. Secondly, we introduced the new UFFDIO_WRITEPROTECT API to do page level write protection tracking. Note that we will need to register the memory region with UFFDIO_REGISTER_MODE_WP before that. [peterx@redhat.com: write up the commit message] [peterx@redhat.com: remove useless block, write commit message, check against VM_MAYWRITE rather than VM_WRITE when register] Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jerome Glisse <jglisse@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@fb.com> Link: http://lkml.kernel.org/r/20200220163112.11409-14-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Andrea Arcangeli
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72981e0e7b |
userfaultfd: wp: add UFFDIO_COPY_MODE_WP
This allows UFFDIO_COPY to map pages write-protected. [peterx@redhat.com: switch to VM_WARN_ON_ONCE in mfill_atomic_pte; add brackets around "dst_vma->vm_flags & VM_WRITE"; fix wordings in comments and commit messages] Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jerome Glisse <jglisse@redhat.com> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@fb.com> Link: http://lkml.kernel.org/r/20200220163112.11409-6-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
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3e69ad081c |
mm/userfaultfd: honor FAULT_FLAG_KILLABLE in fault path
Userfaultfd fault path was by default killable even if the caller does not have FAULT_FLAG_KILLABLE. That makes sense before in that when with gup we don't have FAULT_FLAG_KILLABLE properly set before. Now after previous patch we've got FAULT_FLAG_KILLABLE applied even for gup code so it should also make sense to let userfaultfd to honor the FAULT_FLAG_KILLABLE. Because we're unconditionally setting FAULT_FLAG_KILLABLE in gup code right now, this patch should have no functional change. It also cleaned the code a little bit by introducing some helpers. Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Brian Geffon <bgeffon@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Matthew Wilcox <willy@infradead.org> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Link: http://lkml.kernel.org/r/20200220160300.9941-1-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
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c270a7eedc |
mm: introduce FAULT_FLAG_INTERRUPTIBLE
handle_userfaultfd() is currently the only one place in the kernel page fault procedures that can respond to non-fatal userspace signals. It was trying to detect such an allowance by checking against USER & KILLABLE flags, which was "un-official". In this patch, we introduced a new flag (FAULT_FLAG_INTERRUPTIBLE) to show that the fault handler allows the fault procedure to respond even to non-fatal signals. Meanwhile, add this new flag to the default fault flags so that all the page fault handlers can benefit from the new flag. With that, replacing the userfault check to this one. Since the line is getting even longer, clean up the fault flags a bit too to ease TTY users. Although we've got a new flag and applied it, we shouldn't have any functional change with this patch so far. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Brian Geffon <bgeffon@google.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Matthew Wilcox <willy@infradead.org> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Link: http://lkml.kernel.org/r/20200220195348.16302-1-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Peter Xu
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ef429ee740 |
userfaultfd: don't retake mmap_sem to emulate NOPAGE
This patch removes the risk path in handle_userfault() then we will be sure that the callers of handle_mm_fault() will know that the VMAs might have changed. Meanwhile with previous patch we don't lose responsiveness as well since the core mm code now can handle the nonfatal userspace signals even if we return VM_FAULT_RETRY. Suggested-by: Andrea Arcangeli <aarcange@redhat.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Brian Geffon <bgeffon@google.com> Reviewed-by: Jerome Glisse <jglisse@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: David Hildenbrand <david@redhat.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Matthew Wilcox <willy@infradead.org> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Link: http://lkml.kernel.org/r/20200220160234.9646-1-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linus Torvalds
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596cf45cbf |
Merge branch 'akpm' (patches from Andrew)
Merge updates from Andrew Morton: "Incoming: - a small number of updates to scripts/, ocfs2 and fs/buffer.c - most of MM I still have quite a lot of material (mostly not MM) staged after linux-next due to -next dependencies. I'll send those across next week as the preprequisites get merged up" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (135 commits) mm/page_io.c: annotate refault stalls from swap_readpage mm/Kconfig: fix trivial help text punctuation mm/Kconfig: fix indentation mm/memory_hotplug.c: remove __online_page_set_limits() mm: fix typos in comments when calling __SetPageUptodate() mm: fix struct member name in function comments mm/shmem.c: cast the type of unmap_start to u64 mm: shmem: use proper gfp flags for shmem_writepage() mm/shmem.c: make array 'values' static const, makes object smaller userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK fs/userfaultfd.c: wp: clear VM_UFFD_MISSING or VM_UFFD_WP during userfaultfd_register() userfaultfd: wrap the common dst_vma check into an inlined function userfaultfd: remove unnecessary WARN_ON() in __mcopy_atomic_hugetlb() userfaultfd: use vma_pagesize for all huge page size calculation mm/madvise.c: use PAGE_ALIGN[ED] for range checking mm/madvise.c: replace with page_size() in madvise_inject_error() mm/mmap.c: make vma_merge() comment more easy to understand mm/hwpoison-inject: use DEFINE_DEBUGFS_ATTRIBUTE to define debugfs fops autonuma: reduce cache footprint when scanning page tables autonuma: fix watermark checking in migrate_balanced_pgdat() ... |
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Mike Rapoport
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3c1c24d91f |
userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK
A while ago Andy noticed (http://lkml.kernel.org/r/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com) that UFFD_FEATURE_EVENT_FORK used by an unprivileged user may have security implications. As the first step of the solution the following patch limits the availably of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE. The usage of CAP_SYS_PTRACE ensures compatibility with CRIU. Yet, if there are other users of non-cooperative userfaultfd that run without CAP_SYS_PTRACE, they would be broken :( Current implementation of UFFD_FEATURE_EVENT_FORK modifies the file descriptor table from the read() implementation of uffd, which may have security implications for unprivileged use of the userfaultfd. Limit availability of UFFD_FEATURE_EVENT_FORK only for callers that have CAP_SYS_PTRACE. Link: http://lkml.kernel.org/r/1572967777-8812-2-git-send-email-rppt@linux.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Daniel Colascione <dancol@google.com> Cc: Jann Horn <jannh@google.com> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Nick Kralevich <nnk@google.com> Cc: Nosh Minwalla <nosh@google.com> Cc: Pavel Emelyanov <ovzxemul@gmail.com> Cc: Tim Murray <timmurray@google.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Andrea Arcangeli
|
9d4678eb17 |
fs/userfaultfd.c: wp: clear VM_UFFD_MISSING or VM_UFFD_WP during userfaultfd_register()
If the registration is repeated without VM_UFFD_MISSING or VM_UFFD_WP they need to be cleared. Currently setting UFFDIO_REGISTER_MODE_WP returns -EINVAL, so this patch is a noop until the UFFDIO_REGISTER_MODE_WP support is applied. Link: http://lkml.kernel.org/r/20191004232834.GP13922@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Wei Yang <richardw.yang@linux.intel.com> Reviewed-by: Wei Yang <richardw.yang@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
Arnd Bergmann
|
1832f2d8ff |
compat_ioctl: move more drivers to compat_ptr_ioctl
The .ioctl and .compat_ioctl file operations have the same prototype so they can both point to the same function, which works great almost all the time when all the commands are compatible. One exception is the s390 architecture, where a compat pointer is only 31 bit wide, and converting it into a 64-bit pointer requires calling compat_ptr(). Most drivers here will never run in s390, but since we now have a generic helper for it, it's easy enough to use it consistently. I double-checked all these drivers to ensure that all ioctl arguments are used as pointers or are ignored, but are not interpreted as integer values. Acked-by: Jason Gunthorpe <jgg@mellanox.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: David Sterba <dsterba@suse.com> Acked-by: Darren Hart (VMware) <dvhart@infradead.org> Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org> Acked-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> |
||
Andrey Konovalov
|
7d0325749a |
userfaultfd: untag user pointers
This patch is a part of a series that extends kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments. userfaultfd code use provided user pointers for vma lookups, which can only by done with untagged pointers. Untag user pointers in validate_range(). Link: http://lkml.kernel.org/r/cdc59ddd7011012ca2e689bc88c3b65b1ea7e413.1563904656.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Eric Auger <eric.auger@redhat.com> Cc: Felix Kuehling <Felix.Kuehling@amd.com> Cc: Jens Wiklander <jens.wiklander@linaro.org> Cc: Khalid Aziz <khalid.aziz@oracle.com> Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
Oleg Nesterov
|
46d0b24c5e |
userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx
userfaultfd_release() should clear vm_flags/vm_userfaultfd_ctx even if
mm->core_state != NULL.
Otherwise a page fault can see userfaultfd_missing() == T and use an
already freed userfaultfd_ctx.
Link: http://lkml.kernel.org/r/20190820160237.GB4983@redhat.com
Fixes:
|
||
Eric Biggers
|
cbcfa130a9 |
fs/userfaultfd.c: disable irqs for fault_pending and event locks
When IOCB_CMD_POLL is used on a userfaultfd, aio_poll() disables IRQs and takes kioctx::ctx_lock, then userfaultfd_ctx::fd_wqh.lock. This may have to wait for userfaultfd_ctx::fd_wqh.lock to be released by userfaultfd_ctx_read(), which in turn can be waiting for userfaultfd_ctx::fault_pending_wqh.lock or userfaultfd_ctx::event_wqh.lock. But elsewhere the fault_pending_wqh and event_wqh locks are taken with IRQs enabled. Since the IRQ handler may take kioctx::ctx_lock, lockdep reports that a deadlock is possible. Fix it by always disabling IRQs when taking the fault_pending_wqh and event_wqh locks. Commit |
||
Thomas Gleixner
|
20c8ccb197 |
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499
Based on 1 normalized pattern(s): this work is licensed under the terms of the gnu gpl version 2 see the copying file in the top level directory extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 35 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Enrico Weigelt <info@metux.net> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190604081206.797835076@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
|
Peter Xu
|
cefdca0a86 |
userfaultfd/sysctl: add vm.unprivileged_userfaultfd
Userfaultfd can be misued to make it easier to exploit existing use-after-free (and similar) bugs that might otherwise only make a short window or race condition available. By using userfaultfd to stall a kernel thread, a malicious program can keep some state that it wrote, stable for an extended period, which it can then access using an existing exploit. While it doesn't cause the exploit itself, and while it's not the only thing that can stall a kernel thread when accessing a memory location, it's one of the few that never needs privilege. We can add a flag, allowing userfaultfd to be restricted, so that in general it won't be useable by arbitrary user programs, but in environments that require userfaultfd it can be turned back on. Add a global sysctl knob "vm.unprivileged_userfaultfd" to control whether userfaultfd is allowed by unprivileged users. When this is set to zero, only privileged users (root user, or users with the CAP_SYS_PTRACE capability) will be able to use the userfaultfd syscalls. Andrea said: : The only difference between the bpf sysctl and the userfaultfd sysctl : this way is that the bpf sysctl adds the CAP_SYS_ADMIN capability : requirement, while userfaultfd adds the CAP_SYS_PTRACE requirement, : because the userfaultfd monitor is more likely to need CAP_SYS_PTRACE : already if it's doing other kind of tracking on processes runtime, in : addition of userfaultfd. In other words both syscalls works only for : root, when the two sysctl are opt-in set to 1. [dgilbert@redhat.com: changelog additions] [akpm@linux-foundation.org: documentation tweak, per Mike] Link: http://lkml.kernel.org/r/20190319030722.12441-2-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Suggested-by: Andrea Arcangeli <aarcange@redhat.com> Suggested-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Maxime Coquelin <maxime.coquelin@redhat.com> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Pavel Emelyanov <xemul@virtuozzo.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Martin Cracauer <cracauer@cons.org> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Kees Cook <keescook@chromium.org> Cc: Mel Gorman <mgorman@suse.de> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Andrea Arcangeli
|
04f5866e41 |
coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping
The core dumping code has always run without holding the mmap_sem for
writing, despite that is the only way to ensure that the entire vma
layout will not change from under it. Only using some signal
serialization on the processes belonging to the mm is not nearly enough.
This was pointed out earlier. For example in Hugh's post from Jul 2017:
https://lkml.kernel.org/r/alpine.LSU.2.11.1707191716030.2055@eggly.anvils
"Not strictly relevant here, but a related note: I was very surprised
to discover, only quite recently, how handle_mm_fault() may be called
without down_read(mmap_sem) - when core dumping. That seems a
misguided optimization to me, which would also be nice to correct"
In particular because the growsdown and growsup can move the
vm_start/vm_end the various loops the core dump does around the vma will
not be consistent if page faults can happen concurrently.
Pretty much all users calling mmget_not_zero()/get_task_mm() and then
taking the mmap_sem had the potential to introduce unexpected side
effects in the core dumping code.
Adding mmap_sem for writing around the ->core_dump invocation is a
viable long term fix, but it requires removing all copy user and page
faults and to replace them with get_dump_page() for all binary formats
which is not suitable as a short term fix.
For the time being this solution manually covers the places that can
confuse the core dump either by altering the vma layout or the vma flags
while it runs. Once ->core_dump runs under mmap_sem for writing the
function mmget_still_valid() can be dropped.
Allowing mmap_sem protected sections to run in parallel with the
coredump provides some minor parallelism advantage to the swapoff code
(which seems to be safe enough by never mangling any vma field and can
keep doing swapins in parallel to the core dumping) and to some other
corner case.
In order to facilitate the backporting I added "Fixes: 86039bd3b4e6"
however the side effect of this same race condition in /proc/pid/mem
should be reproducible since before 2.6.12-rc2 so I couldn't add any
other "Fixes:" because there's no hash beyond the git genesis commit.
Because find_extend_vma() is the only location outside of the process
context that could modify the "mm" structures under mmap_sem for
reading, by adding the mmget_still_valid() check to it, all other cases
that take the mmap_sem for reading don't need the new check after
mmget_not_zero()/get_task_mm(). The expand_stack() in page fault
context also doesn't need the new check, because all tasks under core
dumping are frozen.
Link: http://lkml.kernel.org/r/20190325224949.11068-1-aarcange@redhat.com
Fixes:
|
||
|
Peter Xu
|
3cfd22be0a |
userfaultfd: clear flag if remap event not enabled
When the process being tracked does mremap() without UFFD_FEATURE_EVENT_REMAP on the corresponding tracking uffd file handle, we should not generate the remap event, and at the same time we should clear all the uffd flags on the new VMA. Without this patch, we can still have the VM_UFFD_MISSING|VM_UFFD_WP flags on the new VMA even the fault handling process does not even know the existance of the VMA. Link: http://lkml.kernel.org/r/20181211053409.20317-1-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Hugh Dickins <hughd@google.com> Cc: Pavel Emelyanov <xemul@virtuozzo.com> Cc: Pravin Shedge <pravin.shedge4linux@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Eric Biggers
|
ca88042066 |
userfaultfd: convert userfaultfd_ctx::refcount to refcount_t
Reference counters should use refcount_t rather than atomic_t, since the refcount_t implementation can prevent overflows, reducing the exploitability of reference leak bugs. userfaultfd_ctx::refcount is a reference counter with the usual semantics, so convert it to refcount_t. Note: I replaced the BUG() on incrementing a 0 refcount with just refcount_inc(), since part of the semantics of refcount_t is that that incrementing a 0 refcount is not allowed; with CONFIG_REFCOUNT_FULL, refcount_inc() already checks for it and warns. Link: http://lkml.kernel.org/r/20181115003916.63381-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Linus Torvalds
|
792bf4d871 |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"The biggest RCU changes in this cycle were:
- Convert RCU's BUG_ON() and similar calls to WARN_ON() and similar.
- Replace calls of RCU-bh and RCU-sched update-side functions to
their vanilla RCU counterparts. This series is a step towards
complete removal of the RCU-bh and RCU-sched update-side functions.
( Note that some of these conversions are going upstream via their
respective maintainers. )
- Documentation updates, including a number of flavor-consolidation
updates from Joel Fernandes.
- Miscellaneous fixes.
- Automate generation of the initrd filesystem used for rcutorture
testing.
- Convert spin_is_locked() assertions to instead use lockdep.
( Note that some of these conversions are going upstream via their
respective maintainers. )
- SRCU updates, especially including a fix from Dennis Krein for a
bag-on-head-class bug.
- RCU torture-test updates"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (112 commits)
rcutorture: Don't do busted forward-progress testing
rcutorture: Use 100ms buckets for forward-progress callback histograms
rcutorture: Recover from OOM during forward-progress tests
rcutorture: Print forward-progress test age upon failure
rcutorture: Print time since GP end upon forward-progress failure
rcutorture: Print histogram of CB invocation at OOM time
rcutorture: Print GP age upon forward-progress failure
rcu: Print per-CPU callback counts for forward-progress failures
rcu: Account for nocb-CPU callback counts in RCU CPU stall warnings
rcutorture: Dump grace-period diagnostics upon forward-progress OOM
rcutorture: Prepare for asynchronous access to rcu_fwd_startat
torture: Remove unnecessary "ret" variables
rcutorture: Affinity forward-progress test to avoid housekeeping CPUs
rcutorture: Break up too-long rcu_torture_fwd_prog() function
rcutorture: Remove cbflood facility
torture: Bring any extra CPUs online during kernel startup
rcutorture: Add call_rcu() flooding forward-progress tests
rcutorture/formal: Replace synchronize_sched() with synchronize_rcu()
tools/kernel.h: Replace synchronize_sched() with synchronize_rcu()
net/decnet: Replace rcu_barrier_bh() with rcu_barrier()
...
|
||
|
Andrea Arcangeli
|
01e881f5a1 |
userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd
could trigger an harmless false positive WARN_ON. Check the vma is
already registered before checking VM_MAYWRITE to shut off the false
positive warning.
Link: http://lkml.kernel.org/r/20181206212028.18726-2-aarcange@redhat.com
Cc: <stable@vger.kernel.org>
Fixes:
|
||
Ingo Molnar
|
4bbfd7467c |
Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU changes from Paul E. McKenney:
- Convert RCU's BUG_ON() and similar calls to WARN_ON() and similar.
- Replace calls of RCU-bh and RCU-sched update-side functions
to their vanilla RCU counterparts. This series is a step
towards complete removal of the RCU-bh and RCU-sched update-side
functions.
( Note that some of these conversions are going upstream via their
respective maintainers. )
- Documentation updates, including a number of flavor-consolidation
updates from Joel Fernandes.
- Miscellaneous fixes.
- Automate generation of the initrd filesystem used for
rcutorture testing.
- Convert spin_is_locked() assertions to instead use lockdep.
( Note that some of these conversions are going upstream via their
respective maintainers. )
- SRCU updates, especially including a fix from Dennis Krein
for a bag-on-head-class bug.
- RCU torture-test updates.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
||
|
Andrea Arcangeli
|
29ec90660d |
userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas
After the VMA to register the uffd onto is found, check that it has VM_MAYWRITE set before allowing registration. This way we inherit all common code checks before allowing to fill file holes in shmem and hugetlbfs with UFFDIO_COPY. The userfaultfd memory model is not applicable for readonly files unless it's a MAP_PRIVATE. Link: http://lkml.kernel.org/r/20181126173452.26955-4-aarcange@redhat.com Fixes: |
||
Lance Roy
|
456a737896 |
userfaultfd: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements, since it only checks if the current thread holds the lock regardless of whether someone else does. This is also a step towards possibly removing spin_is_locked(). Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <linux-fsdevel@vger.kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> |
||
Christoph Hellwig
|
ae62c16e10 |
userfaultfd: disable irqs when taking the waitqueue lock
userfaultfd contains howe-grown locking of the waitqueue lock, and does not disable interrupts. This relies on the fact that no one else takes it from interrupt context and violates an invariat of the normal waitqueue locking scheme. With aio poll it is easy to trigger other locks that disable interrupts (or are called from interrupt context). Link: http://lkml.kernel.org/r/20181018154101.18750-1-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@vger.kernel.org> [4.19.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
Souptick Joarder
|
2b74030354 |
mm: Change return type int to vm_fault_t for fault handlers
Use new return type vm_fault_t for fault handler. For now, this is just
documenting that the function returns a VM_FAULT value rather than an
errno. Once all instances are converted, vm_fault_t will become a
distinct type.
Ref-> commit
|
||
Matthew Wilcox
|
c430d1e848 |
userfaultfd: use fault_wqh lock
The userfaultfd code currently uses the unlocked waitqueue helpers for managing fault_wqh, but instead of holding the waitqueue lock for this waitqueue around these calls, it the waitqueue lock of fault_pending_wq, which is a different waitqueue instance. Given that the waitqueue is not exposed to the rest of the kernel this actually works ok at the moment, but prevents the userfaultfd locking rules from being enforced using lockdep. Switch to the internally locked waitqueue helpers instead. This means that the lock inside fault_wqh now nests inside the fault_pending_wqh lock, but that's not a problem since it was entirely unused before. [hch@lst.de: slight changelog updates] [rppt@linux.vnet.ibm.com: spotted changelog spellos] Link: http://lkml.kernel.org/r/20171214152344.6880-3-hch@lst.de Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
Colin Ian King
|
5241d47274 |
fs/userfaultfd.c: remove redundant pointer uwq
Pointer uwq is being assigned but is never used hence it is redundant and can be removed. Cleans up clang warning: warning: variable 'uwq' set but not used [-Wunused-but-set-variable] Link: http://lkml.kernel.org/r/20180717090802.18357-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
Mike Rapoport
|
31e810aa10 |
userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails
The fix in commit |
||
Janosch Frank
|
1e2c043628 |
userfaultfd: hugetlbfs: fix userfaultfd_huge_must_wait() pte access
Use huge_ptep_get() to translate huge ptes to normal ptes so we can
check them with the huge_pte_* functions. Otherwise some architectures
will check the wrong values and will not wait for userspace to bring in
the memory.
Link: http://lkml.kernel.org/r/20180626132421.78084-1-frankja@linux.ibm.com
Fixes:
|
||
|
Mike Rapoport
|
df2cc96e77 |
userfaultfd: prevent non-cooperative events vs mcopy_atomic races
If a process monitored with userfaultfd changes it's memory mappings or
forks() at the same time as uffd monitor fills the process memory with
UFFDIO_COPY, the actual creation of page table entries and copying of
the data in mcopy_atomic may happen either before of after the memory
mapping modifications and there is no way for the uffd monitor to
maintain consistent view of the process memory layout.
For instance, let's consider fork() running in parallel with
userfaultfd_copy():
process | uffd monitor
---------------------------------+------------------------------
fork() | userfaultfd_copy()
... | ...
dup_mmap() | down_read(mmap_sem)
down_write(mmap_sem) | /* create PTEs, copy data */
dup_uffd() | up_read(mmap_sem)
copy_page_range() |
up_write(mmap_sem) |
dup_uffd_complete() |
/* notify monitor */ |
If the userfaultfd_copy() takes the mmap_sem first, the new page(s) will
be present by the time copy_page_range() is called and they will appear
in the child's memory mappings. However, if the fork() is the first to
take the mmap_sem, the new pages won't be mapped in the child's address
space.
If the pages are not present and child tries to access them, the monitor
will get page fault notification and everything is fine. However, if
the pages *are present*, the child can access them without uffd
noticing. And if we copy them into child it'll see the wrong data.
Since we are talking about background copy, we'd need to decide whether
the pages should be copied or not regardless #PF notifications.
Since userfaultfd monitor has no way to determine what was the order,
let's disallow userfaultfd_copy in parallel with the non-cooperative
events. In such case we return -EAGAIN and the uffd monitor can
understand that userfaultfd_copy() clashed with a non-cooperative event
and take an appropriate action.
Link: http://lkml.kernel.org/r/1527061324-19949-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds
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a9a08845e9 |
vfs: do bulk POLL* -> EPOLL* replacement
This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:
for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
done
with de-mangling cleanups yet to come.
NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do. But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.
The next patch from Al will sort out the final differences, and we
should be all done.
Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Eric Biggers
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284cd241a1 |
userfaultfd: convert to use anon_inode_getfd()
Nothing actually calls userfaultfd_file_create() besides the userfaultfd() system call itself. So simplify things by folding it into the system call and using anon_inode_getfd() instead of anon_inode_getfile(). Do the same in resolve_userfault_fork() as well. This removes over 50 lines with no change in functionality. Link: http://lkml.kernel.org/r/20171229212403.22800-1-ebiggers3@gmail.com Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Huang Ying
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a365ac09d3 |
mm, userfaultfd, THP: avoid waiting when PMD under THP migration
If THP migration is enabled, for a VMA handled by userfaultfd, consider
the following situation,
do_page_fault()
__do_huge_pmd_anonymous_page()
handle_userfault()
userfault_msg()
/* a huge page is allocated and mapped at fault address */
/* the huge page is under migration, leaves migration entry
in page table */
userfaultfd_must_wait()
/* return true because !pmd_present() */
/* may wait in loop until fatal signal */
That is, it may be possible for userfaultfd_must_wait() encounters a PMD
entry which is !pmd_none() && !pmd_present(). In the current
implementation, we will wait for such PMD entries, which may cause
unnecessary waiting, and potential soft lockup.
This is fixed via avoiding to wait when !pmd_none() && !pmd_present(),
only wait when pmd_none().
This may be not a problem in practice, because userfaultfd_must_wait()
is always called with mm->mmap_sem read-locked. mremap() will
write-lock mm->mmap_sem. And UFFDIO_COPY doesn't support to copy THP
mapping. But the change introduced still makes the code more correct,
and makes the PMD and PTE code more consistent.
Link: http://lkml.kernel.org/r/20171207011752.3292-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.UK>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds
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168fe32a07 |
Merge branch 'misc.poll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull poll annotations from Al Viro: "This introduces a __bitwise type for POLL### bitmap, and propagates the annotations through the tree. Most of that stuff is as simple as 'make ->poll() instances return __poll_t and do the same to local variables used to hold the future return value'. Some of the obvious brainos found in process are fixed (e.g. POLLIN misspelled as POLL_IN). At that point the amount of sparse warnings is low and most of them are for genuine bugs - e.g. ->poll() instance deciding to return -EINVAL instead of a bitmap. I hadn't touched those in this series - it's large enough as it is. Another problem it has caught was eventpoll() ABI mess; select.c and eventpoll.c assumed that corresponding POLL### and EPOLL### were equal. That's true for some, but not all of them - EPOLL### are arch-independent, but POLL### are not. The last commit in this series separates userland POLL### values from the (now arch-independent) kernel-side ones, converting between them in the few places where they are copied to/from userland. AFAICS, this is the least disruptive fix preserving poll(2) ABI and making epoll() work on all architectures. As it is, it's simply broken on sparc - try to give it EPOLLWRNORM and it will trigger only on what would've triggered EPOLLWRBAND on other architectures. EPOLLWRBAND and EPOLLRDHUP, OTOH, are never triggered at all on sparc. With this patch they should work consistently on all architectures" * 'misc.poll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (37 commits) make kernel-side POLL... arch-independent eventpoll: no need to mask the result of epi_item_poll() again eventpoll: constify struct epoll_event pointers debugging printk in sg_poll() uses %x to print POLL... bitmap annotate poll(2) guts 9p: untangle ->poll() mess ->si_band gets POLL... bitmap stored into a user-visible long field ring_buffer_poll_wait() return value used as return value of ->poll() the rest of drivers/*: annotate ->poll() instances media: annotate ->poll() instances fs: annotate ->poll() instances ipc, kernel, mm: annotate ->poll() instances net: annotate ->poll() instances apparmor: annotate ->poll() instances tomoyo: annotate ->poll() instances sound: annotate ->poll() instances acpi: annotate ->poll() instances crypto: annotate ->poll() instances block: annotate ->poll() instances x86: annotate ->poll() instances ... |
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Andrea Arcangeli
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0cbb4b4f4c |
userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails
The previous fix in commit
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