drm/amd/display: Fix NULL pointer dereference in dcn401_init_hw()

Overview

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

drm/amd/display: Fix NULL pointer dereference in dcn401_init_hw()

dcn401_init_hw() assumes that update_bw_bounding_box() is valid when entering the update path. However, the existing condition:

((!fams2_enable && update_bw_bounding_box) || freq_changed)

does not guarantee this, as the freq_changed branch can evaluate to true independently of the callback pointer.

This can result in calling update_bw_bounding_box() when it is NULL.

Fix this by separating the update condition from the pointer checks and ensuring the callback, dc->clk_mgr, and bw_params are validated before use.

Fixes the below: ../dc/hwss/dcn401/dcn401_hwseq.c:367 dcn401_init_hw() error: we previously assumed 'dc->res_pool->funcs->update_bw_bounding_box' could be null (see line 362)

(cherry picked from commit 86117c5ab42f21562fedb0a64bffea3ee5fcd477)

Affected

• Linux >= ca0fb243c3bb53dbbd71d16c76f319bf923ee3d4 < fcc51c81cb472eb460310c477460356dc4845ff7
• Linux >= ca0fb243c3bb53dbbd71d16c76f319bf923ee3d4 < 10c13c111d0d7f8e101c742feff264fc98e3f9f7
• Linux >= ca0fb243c3bb53dbbd71d16c76f319bf923ee3d4 < 2d4a6f0702c5211e0be8b688c5fc24f082ec74d6
• Linux >= ca0fb243c3bb53dbbd71d16c76f319bf923ee3d4 < e927b36ae18b66b49219eaa9f46edc7b4fdbb25e
• Linux e13689793b9c0e7b5749954e77f5f85e68fe7138
• Linux >= 6.11.3 < 6.12
• Linux 6.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.