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Filename Latest commit message Latest commit date
Jann Horn dc2ce1dfce filelock: Remove locks reliably when fcntl/close race is detected
commit 3cad1bc010416c6dd780643476bc59ed742436b9 upstream.

When fcntl_setlk() races with close(), it removes the created lock with
do_lock_file_wait().
However, LSMs can allow the first do_lock_file_wait() that created the lock
while denying the second do_lock_file_wait() that tries to remove the lock.
In theory (but AFAIK not in practice), posix_lock_file() could also fail to
remove a lock due to GFP_KERNEL allocation failure (when splitting a range
in the middle).

After the bug has been triggered, use-after-free reads will occur in
lock_get_status() when userspace reads /proc/locks. This can likely be used
to read arbitrary kernel memory, but can't corrupt kernel memory.
This only affects systems with SELinux / Smack / AppArmor / BPF-LSM in
enforcing mode and only works from some security contexts.

Fix it by calling locks_remove_posix() instead, which is designed to
reliably get rid of POSIX locks associated with the given file and
files_struct and is also used by filp_flush().

Fixes: c293621bbf ("[PATCH] stale POSIX lock handling")
Cc: stable@kernel.org
Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2563
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20240702-fs-lock-recover-2-v1-1-edd456f63789@google.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
[stable fixup: ->c.flc_type was ->fl_type in older kernels]
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-07-27 10:38:28 +02:00
arch ARM: davinci: Convert comma to semicolon 2024-07-18 11:40:54 +02:00
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drivers i2c: rcar: bring hardware to known state when probing 2024-07-18 11:40:56 +02:00
fs filelock: Remove locks reliably when fcntl/close race is detected 2024-07-27 10:38:28 +02:00
include SUNRPC: Fix RPC client cleaned up the freed pipefs dentries 2024-07-18 11:40:56 +02:00
init
ipc
kernel mm: optimize the redundant loop of mm_update_owner_next() 2024-07-18 11:40:51 +02:00
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mm Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again" 2024-07-18 11:40:51 +02:00
net tcp: avoid too many retransmit packets 2024-07-18 11:40:56 +02:00
samples
scripts gcc-plugins: Rename last_stmt() for GCC 14+ 2024-07-27 10:38:28 +02:00
security
sound ALSA: hda/realtek: Limit mic boost on VAIO PRO PX 2024-07-18 11:40:55 +02:00
tools selftests: make order checking verbose in msg_zerocopy selftest 2024-07-18 11:40:50 +02:00
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Makefile Linux 5.4.280 2024-07-18 11:40:56 +02:00
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.