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Paolo Bonzini 83d42c2586 KVM: do not assume PTE is writable after follow_pfn 
commit bd2fae8da794b55bf2ac02632da3a151b10e664c upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-26 10:13:01 +01:00
arch KVM: x86: Zap the oldest MMU pages, not the newest 2021-02-26 10:13:00 +01:00
block bfq-iosched: Revert "bfq: Fix computation of shallow depth" 2021-02-17 11:02:24 +01:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: xor - Fix divide error in do_xor_speed() 2021-01-27 11:54:52 +01:00
Documentation ovl: implement volatile-specific fsync error behaviour 2021-02-10 09:29:16 +01:00
drivers hwmon: (dell-smm) Add XPS 15 L502X to fan control blacklist 2021-02-26 10:13:00 +01:00
fs mm: simplify follow_pte{,pmd} 2021-02-26 10:13:00 +01:00
include mm: simplify follow_pte{,pmd} 2021-02-26 10:13:00 +01:00
init fgraph: Initialize tracing_graph_pause at task creation 2021-02-10 09:29:16 +01:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel bpf: Fix truncation handling for mod32 dst reg wrt zero 2021-02-26 10:12:59 +01:00
lib udp: fix skb_copy_and_csum_datagram with odd segment sizes 2021-02-17 11:02:28 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm: simplify follow_pte{,pmd} 2021-02-26 10:13:00 +01:00
net RDMA: Lift ibdev_to_node from rds to common code 2021-02-26 10:12:59 +01:00
samples samples/bpf: Fix possible hang in xdpsock with multiple threads 2020-12-30 11:53:49 +01:00
scripts scripts: set proper OpenSSL include dir also for sign-file 2021-02-17 11:02:28 +01:00
security cap: fix conversions on getxattr 2021-02-17 11:02:22 +01:00
sound ASoC: Intel: sof_sdw: set proper flags for Dell TGL-H SKU 0A5E 2021-02-13 13:55:07 +01:00
tools selftests: txtimestamp: fix compilation issue 2021-02-17 11:02:26 +01:00
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 2021-02-26 10:13:01 +01:00
.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 mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10.18 2021-02-23 15:53:25 +01:00
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.