Subject: CVE-2024-35876: x86/mce: Make sure to grab mce_sysfs_mutex in set_bank()

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

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

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

x86/mce: Make sure to grab mce_sysfs_mutex in set_bank()

Modifying a MCA bank's MCA_CTL bits which control which error types to
be reported is done over

  /sys/devices/system/machinecheck/
  ├── machinecheck0
  │   ├── bank0
  │   ├── bank1
  │   ├── bank10
  │   ├── bank11
  ...

sysfs nodes by writing the new bit mask of events to enable.

When the write is accepted, the kernel deletes all current timers and
reinits all banks.

Doing that in parallel can lead to initializing a timer which is already
armed and in the timer wheel, i.e., in use already:

  ODEBUG: init active (active state 0) object: ffff888063a28000 object
  type: timer_list hint: mce_timer_fn+0x0/0x240 arch/x86/kernel/cpu/mce/core.c:2642
  WARNING: CPU: 0 PID: 8120 at lib/debugobjects.c:514
  debug_print_object+0x1a0/0x2a0 lib/debugobjects.c:514

Fix that by grabbing the sysfs mutex as the rest of the MCA sysfs code
does.

Reported by: Yue Sun <[email-masked]>
Reported by: xingwei lee <[email-masked]>

The Linux kernel CVE team has assigned CVE-2024-35876 to this issue.

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

	Fixed in 5.4.274 with commit 976b1b2680fb
	Fixed in 5.10.215 with commit f5e65b782f3e
	Fixed in 5.15.154 with commit f860595512ff
	Fixed in 6.1.85 with commit 20a915154ccb
	Fixed in 6.6.26 with commit 5a02df3e9247
	Fixed in 6.8.5 with commit 32223b0b60d5
	Fixed in 6.9 with commit 3ddf944b32f8

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-2024-35876
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:
	arch/x86/kernel/cpu/mce/core.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/976b1b2680fb4c01aaf05a0623288d87619a6c93
	https://git.kernel.org/stable/c/f5e65b782f3e07324b9a8fa3cdaee422f057c758
	https://git.kernel.org/stable/c/f860595512ff5c05a29fa4d64169c3fd1186b8cf
	https://git.kernel.org/stable/c/20a915154ccb88da08986ab6c9fc4c1cf6259de2
	https://git.kernel.org/stable/c/5a02df3e92470efd589712925b5c722e730276a0
	https://git.kernel.org/stable/c/32223b0b60d53f49567fc501f91ca076ae96be6b
	https://git.kernel.org/stable/c/3ddf944b32f88741c303f0b21459dbb3872b8bc5