Subject: CVE-2024-49977: net: stmmac: Fix zero-division error when disabling tc cbs

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

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

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

net: stmmac: Fix zero-division error when disabling tc cbs

The commit b8c43360f6e4 ("net: stmmac: No need to calculate speed divider
when offload is disabled") allows the "port_transmit_rate_kbps" to be
set to a value of 0, which is then passed to the "div_s64" function when
tc-cbs is disabled. This leads to a zero-division error.

When tc-cbs is disabled, the idleslope, sendslope, and credit values the
credit values are not required to be configured. Therefore, adding a return
statement after setting the txQ mode to DCB when tc-cbs is disabled would
prevent a zero-division error.

The Linux kernel CVE team has assigned CVE-2024-49977 to this issue.

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

	Issue introduced in 5.10.221 with commit b4bca4722fda and fixed in 5.10.227 with commit e33fe25b1efe
	Issue introduced in 5.15.162 with commit 2145583e5995 and fixed in 5.15.168 with commit b0da9504a528
	Issue introduced in 6.1.96 with commit 521d42a1c24d and fixed in 6.1.113 with commit 5d43e1ad4567
	Issue introduced in 6.6.36 with commit a71b686418ee and fixed in 6.6.55 with commit 03582f475242
	Issue introduced in 6.10 with commit b8c43360f6e4 and fixed in 6.10.14 with commit e297a2bf56d1
	Issue introduced in 6.10 with commit b8c43360f6e4 and fixed in 6.11.3 with commit 837d9df9c079
	Issue introduced in 6.10 with commit b8c43360f6e4 and fixed in 6.12-rc1 with commit 675faf5a14c1
	Issue introduced in 6.9.7 with commit f01782804147

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-2024-49977
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:
	drivers/net/ethernet/stmicro/stmmac/stmmac_tc.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/e33fe25b1efe4f2e6a5858786dbc82ae4c44ed4c
	https://git.kernel.org/stable/c/b0da9504a528f05f97d926b4db74ff21917a33e9
	https://git.kernel.org/stable/c/5d43e1ad4567d67af2b42d3ab7c14152ffed25c6
	https://git.kernel.org/stable/c/03582f4752427f60817d896f1a827aff772bd31e
	https://git.kernel.org/stable/c/e297a2bf56d12fd7f91a0c209eb6ea84361f3368
	https://git.kernel.org/stable/c/837d9df9c0792902710149d1a5e0991520af0f93
	https://git.kernel.org/stable/c/675faf5a14c14a2be0b870db30a70764df81e2df