Subject: CVE-2024-39291: drm/amdgpu: Fix buffer size in gfx_v9_4_3_init_ cp_compute_microcode() and rlc_microcode()

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

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

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

drm/amdgpu: Fix buffer size in gfx_v9_4_3_init_ cp_compute_microcode() and rlc_microcode()

The function gfx_v9_4_3_init_microcode in gfx_v9_4_3.c was generating
about potential truncation of output when using the snprintf function.
The issue was due to the size of the buffer 'ucode_prefix' being too
small to accommodate the maximum possible length of the string being
written into it.

The string being written is "amdgpu/%s_mec.bin" or "amdgpu/%s_rlc.bin",
where %s is replaced by the value of 'chip_name'. The length of this
string without the %s is 16 characters. The warning message indicated
that 'chip_name' could be up to 29 characters long, resulting in a total
of 45 characters, which exceeds the buffer size of 30 characters.

To resolve this issue, the size of the 'ucode_prefix' buffer has been
reduced from 30 to 15. This ensures that the maximum possible length of
the string being written into the buffer will not exceed its size, thus
preventing potential buffer overflow and truncation issues.

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c: In function ‘gfx_v9_4_3_early_init’:
drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c:379:52: warning: ‘%s’ directive output may be truncated writing up to 29 bytes into a region of size 23 [-Wformat-truncation=]
  379 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_rlc.bin", chip_name);
      |                                                    ^~
......
  439 |         r = gfx_v9_4_3_init_rlc_microcode(adev, ucode_prefix);
      |                                                 ~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c:379:9: note: ‘snprintf’ output between 16 and 45 bytes into a destination of size 30
  379 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_rlc.bin", chip_name);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c:413:52: warning: ‘%s’ directive output may be truncated writing up to 29 bytes into a region of size 23 [-Wformat-truncation=]
  413 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_mec.bin", chip_name);
      |                                                    ^~
......
  443 |         r = gfx_v9_4_3_init_cp_compute_microcode(adev, ucode_prefix);
      |                                                        ~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c:413:9: note: ‘snprintf’ output between 16 and 45 bytes into a destination of size 30
  413 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_mec.bin", chip_name);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Linux kernel CVE team has assigned CVE-2024-39291 to this issue.

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

	Issue introduced in 6.5 with commit 86301129698b and fixed in 6.6.33 with commit 19bd9537b6bc
	Issue introduced in 6.5 with commit 86301129698b and fixed in 6.9.4 with commit f1b6a016dfa4
	Issue introduced in 6.5 with commit 86301129698b and fixed in 6.10 with commit acce6479e30f

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-2024-39291
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/gpu/drm/amd/amdgpu/gfx_v9_4_3.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/19bd9537b6bc1c882df25206c15917214d8e9460
	https://git.kernel.org/stable/c/f1b6a016dfa45cedc080d36fa5d6f22237d80e8b
	https://git.kernel.org/stable/c/acce6479e30f73ab0872e93a75aed1fb791d04ec