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Paolo Bonzini bd2fae8da7 KVM: do not assume PTE is writable after follow_pfn 
In order to convert an HVA to a PFN, KVM usually tries to use
the get_user_pages family of functinso.  This however is not
possible for VM_IO vmas; in that case, KVM instead uses follow_pfn.

In doing this however KVM loses the information on whether the
PFN is writable.  That is usually not a problem because the main
use of VM_IO vmas with KVM is for BARs in PCI device assignment,
however it is a bug.  To fix it, use follow_pte and check pte_write
while under the protection of the PTE lock.  The information can
be used to fail hva_to_pfn_remapped or passed back to the
caller via *writable.

Usage of follow_pfn was introduced in commit add6a0cd1c ("KVM: MMU: try to fix
up page faults before giving up", 2016-07-05); however, even older version
have the same issue, all the way back to commit 2e2e3738af ("KVM:
Handle vma regions with no backing page", 2008-07-20), as they also did
not check whether the PFN was writable.

Fixes: 2e2e3738af ("KVM: Handle vma regions with no backing page")
Reported-by: David Stevens <stevensd@google.com>
Cc: 3pvd@google.com
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-02-04 05:27:14 -05:00
arch KVM: x86/mmu: Fix TDP MMU zap collapsible SPTEs 2021-02-04 04:38:53 -05:00
block block-5.11-2021-01-10 2021-01-10 12:53:08 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Char/Misc driver fixes for 5.11-rc3 2021-01-10 12:24:33 -08:00
Documentation KVM: Documentation: Fix documentation for nested. 2021-01-28 13:03:14 -05:00
drivers SCSI fixes on 20210110 2021-01-10 13:17:21 -08:00
fs block-5.11-2021-01-10 2021-01-10 12:53:08 -08:00
include block-5.11-2021-01-10 2021-01-10 12:53:08 -08:00
init Revert "init/console: Use ttynull as a fallback when there is no console" 2021-01-08 11:02:18 -08:00
ipc Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
kernel Staging driver fixes for 5.11-rc3 2021-01-10 12:28:07 -08:00
lib Kbuild fixes for v5.11 2021-01-10 13:24:55 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm: make wait_on_page_writeback() wait for multiple pending writebacks 2021-01-05 11:33:00 -08:00
net nexthop: Bounce NHA_GATEWAY in FDB nexthop groups 2021-01-07 18:47:18 -08:00
samples ARM: SoC drivers for v5.11 2020-12-16 16:38:41 -08:00
scripts Kbuild fixes for v5.11 2021-01-10 13:24:55 -08:00
security Provide a fix for the incorrect handling of privilege 2020-12-24 14:08:43 -08:00
sound sound fixes for 5.11-rc3 2021-01-05 13:25:49 -08:00
tools linux-kselftest-kunit-fixes-5.11-rc3 2021-01-08 17:18:50 -08:00
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: do not assume PTE is writable after follow_pfn 2021-02-04 05:27:14 -05:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap RDMA 5.11 pull request 2020-12-16 13:42:26 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-11 22:29:38 -08:00
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 Kbuild fixes for v5.11 2021-01-10 13:24:55 -08:00
Makefile Linux 5.11-rc3 2021-01-10 14:34:50 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.