Affected: Linux

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

drm/amd/display: avoid NPD when ASIC does not support DMUB

ctx->dmub_srv will de NULL if the ASIC does not support DMUB, which is tested in dm_dmub_sw_init.

However, it will be dereferenced in dmub_hw_lock_mgr_cmd if should_use_dmub_lock returns true.

This has been the case since dmub support has been added for PSR1.

Fix this by checking for dmub_srv in should_use_dmub_lock.

[ 37.440832] BUG: kernel NULL pointer dereference, address: 0000000000000058 [ 37.447808] #PF: supervisor read access in kernel mode [ 37.452959] #PF: error_code(0x0000) - not-present page [ 37.458112] PGD 0 P4D 0 [ 37.460662] Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI [ 37.465553] CPU: 2 UID: 1000 PID: 1745 Comm: DrmThread Not tainted 6.14.0-rc1-00003-gd62e938120f0 #23 99720e1cb1e0fc4773b8513150932a07de3c6e88 [ 37.478324] Hardware name: Google Morphius/Morphius, BIOS Google_Morphius.13434.858.0 10/26/2023 [ 37.487103] RIP: 0010:dmub_hw_lock_mgr_cmd+0x77/0xb0 [ 37.492074] Code: 44 24 0e 00 00 00 00 48 c7 04 24 45 00 00 0c 40 88 74 24 0d 0f b6 02 88 44 24 0c 8b 01 89 44 24 08 85 f6 75 05 c6 44 24 0e 01 <48> 8b 7f 58 48 89 e6 ba 01 00 00 00 e8 08 3c 2a 00 65 48 8b 04 5 [ 37.510822] RSP: 0018:ffff969442853300 EFLAGS: 00010202 [ 37.516052] RAX: 0000000000000000 RBX: ffff92db03000000 RCX: ffff969442853358 [ 37.523185] RDX: ffff969442853368 RSI: 0000000000000001 RDI: 0000000000000000 [ 37.530322] RBP: 0000000000000…