Subject: CVE-2024-49960: ext4: fix timer use-after-free on failed mount

From: Greg Kroah-Hartman <[email-masked]>

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

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

ext4: fix timer use-after-free on failed mount

Syzbot has found an ODEBUG bug in ext4_fill_super

The del_timer_sync function cancels the s_err_report timer,
which reminds about filesystem errors daily. We should
guarantee the timer is no longer active before kfree(sbi).

When filesystem mounting fails, the flow goes to failed_mount3,
where an error occurs when ext4_stop_mmpd is called, causing
a read I/O failure. This triggers the ext4_handle_error function
that ultimately re-arms the timer,
leaving the s_err_report timer active before kfree(sbi) is called.

Fix the issue by canceling the s_err_report timer after calling ext4_stop_mmpd.

The Linux kernel CVE team has assigned CVE-2024-49960 to this issue.

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

	Fixed in 6.6.55 with commit 9203817ba46e
	Fixed in 6.10.14 with commit fa78fb51d396
	Fixed in 6.11.3 with commit b85569585d01
	Fixed in 6.12-rc1 with commit 0ce160c5bdb6

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-2024-49960
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/ext4/super.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/9203817ba46ebba7c865c8de2aba399537b6e891
	https://git.kernel.org/stable/c/fa78fb51d396f4f2f80f8e96a3b1516f394258be
	https://git.kernel.org/stable/c/b85569585d0154d4db1e4f9e3e6a4731d407feb0
	https://git.kernel.org/stable/c/0ce160c5bdb67081a62293028dc85758a8efb22a