Subject: CVE-2024-42255: tpm: Use auth only after NULL check in tpm_buf_check_hmac_response()

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

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

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

tpm: Use auth only after NULL check in tpm_buf_check_hmac_response()

Dereference auth after NULL check in tpm_buf_check_hmac_response().
Otherwise, unless tpm2_sessions_init() was called, a call can cause NULL
dereference, when TCG_TPM2_HMAC is enabled.

[jarkko: adjusted the commit message.]

The Linux kernel CVE team has assigned CVE-2024-42255 to this issue.

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

	Issue introduced in 6.10 with commit 7ca110f2679b and fixed in 6.10.1 with commit b9afbb9a0c73
	Issue introduced in 6.10 with commit 7ca110f2679b and fixed in 6.11 with commit 7dc357d343f1

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-2024-42255
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/char/tpm/tpm2-sessions.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/b9afbb9a0c734197c59c43610071041044bf1562
	https://git.kernel.org/stable/c/7dc357d343f134bf59815ff6098b93503ec8a23b