Subject: CVE-2022-48648: sfc: fix null pointer dereference in efx_hard_start_xmit

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

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

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

sfc: fix null pointer dereference in efx_hard_start_xmit

Trying to get the channel from the tx_queue variable here is wrong
because we can only be here if tx_queue is NULL, so we shouldn't
dereference it. As the above comment in the code says, this is very
unlikely to happen, but it's wrong anyway so let's fix it.

I hit this issue because of a different bug that caused tx_queue to be
NULL. If that happens, this is the error message that we get here:
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
  [...]
  RIP: 0010:efx_hard_start_xmit+0x153/0x170 [sfc]

The Linux kernel CVE team has assigned CVE-2022-48648 to this issue.

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

	Issue introduced in 5.10 with commit 12804793b17c and fixed in 5.10.146 with commit b3b41d4d95d3
	Issue introduced in 5.10 with commit 12804793b17c and fixed in 5.15.71 with commit 8547c7bfc061
	Issue introduced in 5.10 with commit 12804793b17c and fixed in 5.19.12 with commit b3b952168ee1
	Issue introduced in 5.10 with commit 12804793b17c and fixed in 6.0 with commit 0a242eb2913a

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-2022-48648
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/sfc/tx.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/b3b41d4d95d3822b2e459ecbc80d030ea6aec5e7
	https://git.kernel.org/stable/c/8547c7bfc0617e7184e4da65b9b96681fcfe9998
	https://git.kernel.org/stable/c/b3b952168ee1f220ba729fa100fd9d5aa752eb03
	https://git.kernel.org/stable/c/0a242eb2913a4aa3d6fbdb86559f27628e9466f3