Subject: CVE-2024-35925: block: prevent division by zero in blk_rq_stat_sum()

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

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

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

block: prevent division by zero in blk_rq_stat_sum()

The expression dst->nr_samples + src->nr_samples may
have zero value on overflow. It is necessary to add
a check to avoid division by zero.

Found by Linux Verification Center (linuxtesting.org) with Svace.

The Linux kernel CVE team has assigned CVE-2024-35925 to this issue.

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

	Fixed in 4.19.312 with commit 6a55dab4ac95
	Fixed in 5.4.274 with commit edd073c78d2b
	Fixed in 5.10.215 with commit b0cb5564c3e8
	Fixed in 5.15.155 with commit 21e7d72d0cfc
	Fixed in 6.1.86 with commit 512a01da7134
	Fixed in 6.6.27 with commit 5f7fd6aa4c48
	Fixed in 6.8.6 with commit 98ddf2604ade
	Fixed in 6.9 with commit 93f52fbeaf4b

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-2024-35925
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:
	block/blk-stat.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/6a55dab4ac956deb23690eedd74e70b892a378e7
	https://git.kernel.org/stable/c/edd073c78d2bf48c5b8bf435bbc3d61d6e7c6c14
	https://git.kernel.org/stable/c/b0cb5564c3e8e0ee0a2d28c86fa7f02e82d64c3c
	https://git.kernel.org/stable/c/21e7d72d0cfcbae6042d498ea2e6f395311767f8
	https://git.kernel.org/stable/c/512a01da7134bac8f8b373506011e8aaa3283854
	https://git.kernel.org/stable/c/5f7fd6aa4c4877d77133ea86c14cf256f390b2fe
	https://git.kernel.org/stable/c/98ddf2604ade2d954bf5ec193600d5274a43fd68
	https://git.kernel.org/stable/c/93f52fbeaf4b676b21acfe42a5152620e6770d02