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Vitaly Kuznetsov 77377064c3 KVM: ioapic: break infinite recursion on lazy EOI 
During shutdown the IOAPIC trigger mode is reset to edge triggered
while the vfio-pci INTx is still registered with a resampler.
This allows us to get into an infinite loop:

ioapic_set_irq
  -> ioapic_lazy_update_eoi
  -> kvm_ioapic_update_eoi_one
  -> kvm_notify_acked_irq
  -> kvm_notify_acked_gsi
  -> (via irq_acked fn ptr) irqfd_resampler_ack
  -> kvm_set_irq
  -> (via set fn ptr) kvm_set_ioapic_irq
  -> kvm_ioapic_set_irq
  -> ioapic_set_irq

Commit 8be8f932e3 ("kvm: ioapic: Restrict lazy EOI update to
edge-triggered interrupts", 2020-05-04) acknowledges that this recursion
loop exists and tries to avoid it at the call to ioapic_lazy_update_eoi,
but at this point the scenario is already set, we have an edge interrupt
with resampler on the same gsi.

Fortunately, the only user of irq ack notifiers (in addition to resamplefd)
is i8254 timer interrupt reinjection.  These are edge-triggered, so in
principle they would need the call to kvm_ioapic_update_eoi_one from
ioapic_lazy_update_eoi, but they already disable AVIC(*), so they don't
need the lazy EOI behavior.  Therefore, remove the call to
kvm_ioapic_update_eoi_one from ioapic_lazy_update_eoi.

This fixes CVE-2020-27152.  Note that this issue cannot happen with
SR-IOV assigned devices because virtual functions do not have INTx,
only MSI.

Fixes: f458d039db ("kvm: ioapic: Lazy update IOAPIC EOI")
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-10-24 04:42:06 -04:00
arch KVM: ioapic: break infinite recursion on lazy EOI 2020-10-24 04:42:06 -04:00
block block-5.9-2020-09-04 2020-09-04 13:04:51 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-30 15:53:44 -07:00
Documentation Documentation: kvm: fix some typos in cpuid.rst 2020-10-21 17:36:32 -04:00
drivers IOMMU Fixes for Linux v5.9-rc3 2020-09-06 11:58:15 -07:00
fs io_uring-5.9-2020-09-06 2020-09-06 12:10:27 -07:00
include kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
init init: fix error check in clean_path() 2020-09-04 09:16:58 -07:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel Misc fixes: 2020-09-06 10:28:00 -07:00
lib lib: Revert use of fallthrough pseudo-keyword in lib/ 2020-08-24 14:17:44 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm xen: branch for v5.9-rc4 2020-09-06 09:59:27 -07:00
net net/packet: fix overflow in tpacket_rcv 2020-09-04 11:56:02 -07:00
samples treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
scripts Merge branch 'akpm' (patches from Andrew) 2020-09-05 13:28:40 -07:00
security treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
sound sound fixes for 5.9-rc4 2020-09-04 12:05:25 -07:00
tools Merge branch 'kvm-fixes' into 'next' 2020-10-21 18:05:58 -04:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2020-09-01 12:53:42 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap Merge branch 'akpm' (patches from Andrew) 2020-08-21 14:44:48 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS IOMMU Fixes for Linux v5.9-rc3 2020-09-06 11:58:15 -07:00
Makefile Linux 5.9-rc4 2020-09-06 17:11:40 -07:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.