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Amir Goldstein a29b6eb959 locks: fix TOCTOU race when granting write lease
[ Upstream commit d6da19c9ca ]

Thread A trying to acquire a write lease checks the value of i_readcount
and i_writecount in check_conflicting_open() to verify that its own fd
is the only fd referencing the file.

Thread B trying to open the file for read will call break_lease() in
do_dentry_open() before incrementing i_readcount, which leaves a small
window where thread A can acquire the write lease and then thread B
completes the open of the file for read without breaking the write lease
that was acquired by thread A.

Fix this race by incrementing i_readcount before checking for existing
leases, same as the case with i_writecount.

Use a helper put_file_access() to decrement i_readcount or i_writecount
in do_dentry_open() and __fput().

Fixes: 387e3746d0 ("locks: eliminate false positive conflicts for write lease")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-10-26 12:34:58 +02:00
arch x86/cpu: Include the header of init_ia32_feat_ctl()'s prototype 2022-10-26 12:34:45 +02:00
block blk-wbt: call rq_qos_add() after wb_normal is initialized 2022-10-26 12:34:33 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto KEYS: asymmetric: enforce SM2 signature use pkey algo 2022-08-17 14:24:28 +02:00
Documentation fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE 2022-10-26 12:34:27 +02:00
drivers memory: of: Fix refcount leak bug in of_lpddr3_get_ddr_timings() 2022-10-26 12:34:58 +02:00
fs locks: fix TOCTOU race when granting write lease 2022-10-26 12:34:58 +02:00
include once: add DO_ONCE_SLOW() for sleepable contexts 2022-10-26 12:34:49 +02:00
init stack: Declare {randomize_,}kstack_offset to fix Sparse warnings 2022-08-17 14:23:10 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:23:10 +02:00
kernel bpf: Ensure correct locking around vulnerable function find_vpid() 2022-10-26 12:34:44 +02:00
lib once: add DO_ONCE_SLOW() for sleepable contexts 2022-10-26 12:34:49 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/mmap: undo ->mmap() when arch_validate_flags() fails 2022-10-26 12:34:24 +02:00
net once: add DO_ONCE_SLOW() for sleepable contexts 2022-10-26 12:34:49 +02:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts selinux: use "grep -E" instead of "egrep" 2022-10-26 12:34:35 +02:00
security ima: fix blocking of security.ima xattrs of unsupported algorithms 2022-10-26 12:34:35 +02:00
sound ALSA: hda/hdmi: Don't skip notification handling during PM operation 2022-10-26 12:34:57 +02:00
tools selftests/xsk: Avoid use-after-free on ctx 2022-10-26 12:34:41 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: SEV: add cache flush to solve SEV cache incoherency issues 2022-09-23 14:15:52 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 Input: goodix - add a goodix.h header file 2022-07-12 16:34:51 +02:00
Makefile hardening: Remove Clang's enable flag for -ftrivial-auto-var-init=zero 2022-10-26 12:34:28 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.