Subject: CVE-2024-42250: cachefiles: add missing lock protection when polling

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

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

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

cachefiles: add missing lock protection when polling

Add missing lock protection in poll routine when iterating xarray,
otherwise:

Even with RCU read lock held, only the slot of the radix tree is
ensured to be pinned there, while the data structure (e.g. struct
cachefiles_req) stored in the slot has no such guarantee.  The poll
routine will iterate the radix tree and dereference cachefiles_req
accordingly.  Thus RCU read lock is not adequate in this case and
spinlock is needed here.

The Linux kernel CVE team has assigned CVE-2024-42250 to this issue.

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

	Issue introduced in 6.8 with commit b817e22b2e91 and fixed in 6.9.10 with commit 8eadcab7f3dd
	Issue introduced in 6.8 with commit b817e22b2e91 and fixed in 6.10 with commit cf5bb09e742a

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-2024-42250
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/cachefiles/daemon.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/97cfd5e20ddc2e33e16ce369626ce76c9a475fd7
	https://git.kernel.org/stable/c/6bb6bd3dd6f382dfd36220d4b210a0c77c066651
	https://git.kernel.org/stable/c/8eadcab7f3dd809edbe5ae20533ff843dfea3a07
	https://git.kernel.org/stable/c/cf5bb09e742a9cf6349127e868329a8f69b7a014