Subject: CVE-2023-52811: scsi: ibmvfc: Remove BUG_ON in the case of an empty event pool

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

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

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

scsi: ibmvfc: Remove BUG_ON in the case of an empty event pool

In practice the driver should never send more commands than are allocated
to a queue's event pool. In the unlikely event that this happens, the code
asserts a BUG_ON, and in the case that the kernel is not configured to
crash on panic returns a junk event pointer from the empty event list
causing things to spiral from there. This BUG_ON is a historical artifact
of the ibmvfc driver first being upstreamed, and it is well known now that
the use of BUG_ON is bad practice except in the most unrecoverable
scenario. There is nothing about this scenario that prevents the driver
from recovering and carrying on.

Remove the BUG_ON in question from ibmvfc_get_event() and return a NULL
pointer in the case of an empty event pool. Update all call sites to
ibmvfc_get_event() to check for a NULL pointer and perfrom the appropriate
failure or recovery action.

The Linux kernel CVE team has assigned CVE-2023-52811 to this issue.

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

	Fixed in 5.15.140 with commit e1d1f79b1929
	Fixed in 6.1.64 with commit 88984ec47927
	Fixed in 6.5.13 with commit d2af4ef80601
	Fixed in 6.6.3 with commit 8bbe784c2ff2
	Fixed in 6.7 with commit b39f2d10b86d

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-2023-52811
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/scsi/ibmvscsi/ibmvfc.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/e1d1f79b1929dce470a5dc9281c574cd58e8c6c0
	https://git.kernel.org/stable/c/88984ec4792766df5a9de7a2ff2b5f281f94c7d4
	https://git.kernel.org/stable/c/d2af4ef80601224b90630c1ddc7cd2c7c8ab4dd8
	https://git.kernel.org/stable/c/8bbe784c2ff28d56ca0c548aaf3e584edc77052d
	https://git.kernel.org/stable/c/b39f2d10b86d0af353ea339e5815820026bca48f