Subject: CVE-2024-49941: gpiolib: Fix potential NULL pointer dereference in gpiod_get_label()

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

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

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

gpiolib: Fix potential NULL pointer dereference in gpiod_get_label()

In `gpiod_get_label()`, it is possible that `srcu_dereference_check()` may
return a NULL pointer, leading to a scenario where `label->str` is accessed
without verifying if `label` itself is NULL.

This patch adds a proper NULL check for `label` before accessing
`label->str`. The check for `label->str != NULL` is removed because
`label->str` can never be NULL if `label` is not NULL.

This fixes the issue where the label name was being printed as `(efault)`
when dumping the sysfs GPIO file when `label == NULL`.

The Linux kernel CVE team has assigned CVE-2024-49941 to this issue.

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

	Issue introduced in 6.9 with commit a86d27693066 and fixed in 6.11.3 with commit 9ee4b907d7a5
	Issue introduced in 6.9 with commit a86d27693066 and fixed in 6.12-rc2 with commit 7b99b5ab8859

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-2024-49941
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/gpio/gpiolib.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/9ee4b907d7a5d7a53b4ff7727c371ff3d44ccbbb
	https://git.kernel.org/stable/c/7b99b5ab885993bff010ebcd93be5e511c56e28a