linux-cve-announce - CVE-2024-53143: fsnotify: Fix ordering of iput() and watched

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Message-ID: <2024120746-CVE-2024-53143-05ed@gregkh>
Date: Sat,  7 Dec 2024 07:40:47 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-53143: fsnotify: Fix ordering of iput() and watched_objects decrement

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

fsnotify: Fix ordering of iput() and watched_objects decrement

Ensure the superblock is kept alive until we're done with iput().
Holding a reference to an inode is not allowed unless we ensure the
superblock stays alive, which fsnotify does by keeping the
watched_objects count elevated, so iput() must happen before the
watched_objects decrement.
This can lead to a UAF of something like sb->s_fs_info in tmpfs, but the
UAF is hard to hit because race orderings that oops are more likely, thanks
to the CHECK_DATA_CORRUPTION() block in generic_shutdown_super().

Also, ensure that fsnotify_put_sb_watched_objects() doesn't call
fsnotify_sb_watched_objects() on a superblock that may have already been
freed, which would cause a UAF read of sb->s_fsnotify_info.

The Linux kernel CVE team has assigned CVE-2024-53143 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.10 with commit d2f277e26f52 and fixed in 6.11.11 with commit 45a8f8232a49
	Issue introduced in 6.10 with commit d2f277e26f52 and fixed in 6.12.2 with commit 83af1cfa10d9
	Issue introduced in 6.10 with commit d2f277e26f52 and fixed in 6.13-rc1 with commit 21d1b618b6b9

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-53143
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	fs/notify/mark.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/45a8f8232a495221ed058191629f5c628f21601a
	https://git.kernel.org/stable/c/83af1cfa10d9aafdabd06b3655e07727f373b434
	https://git.kernel.org/stable/c/21d1b618b6b9da46c5116c640ac4b1cc8d40d63a