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79f9bc5843
Check for a NULL page->mapping before dereferencing the mapping in
page_is_secretmem(), as the page's mapping can be nullified while gup()
is running, e.g. by reclaim or truncation.
BUG: kernel NULL pointer dereference, address: 0000000000000068
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G W
RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0
Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be
RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046
RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900
...
CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0
Call Trace:
get_user_pages_fast_only+0x13/0x20
hva_to_pfn+0xa9/0x3e0
try_async_pf+0xa1/0x270
direct_page_fault+0x113/0xad0
kvm_mmu_page_fault+0x69/0x680
vmx_handle_exit+0xe1/0x5d0
kvm_arch_vcpu_ioctl_run+0xd81/0x1c70
kvm_vcpu_ioctl+0x267/0x670
__x64_sys_ioctl+0x83/0xa0
do_syscall_64+0x56/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Link: https://lkml.kernel.org/r/20211007231502.3552715-1-seanjc@google.com
Fixes: 1507f51255 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reported-by: Darrick J. Wong <djwong@kernel.org>
Reported-by: Stephen <stephenackerman16@gmail.com>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _LINUX_SECRETMEM_H
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#define _LINUX_SECRETMEM_H
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#ifdef CONFIG_SECRETMEM
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extern const struct address_space_operations secretmem_aops;
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static inline bool page_is_secretmem(struct page *page)
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{
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struct address_space *mapping;
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/*
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* Using page_mapping() is quite slow because of the actual call
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* instruction and repeated compound_head(page) inside the
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* page_mapping() function.
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* We know that secretmem pages are not compound and LRU so we can
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* save a couple of cycles here.
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*/
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if (PageCompound(page) || !PageLRU(page))
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return false;
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mapping = (struct address_space *)
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((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
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if (!mapping || mapping != page->mapping)
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return false;
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return mapping->a_ops == &secretmem_aops;
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}
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bool vma_is_secretmem(struct vm_area_struct *vma);
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bool secretmem_active(void);
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#else
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static inline bool vma_is_secretmem(struct vm_area_struct *vma)
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{
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return false;
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}
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static inline bool page_is_secretmem(struct page *page)
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{
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return false;
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}
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static inline bool secretmem_active(void)
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{
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return false;
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}
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#endif /* CONFIG_SECRETMEM */
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#endif /* _LINUX_SECRETMEM_H */
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