Fix below crash by adding a check in the drm_dp_dpcd_access which ensures that aux->transfer was actually initialized earlier.

BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: 0010 [#1] SMP NOPTI RIP: 0010:0x0 Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. RSP: 0018:ffffa8d64225bab8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000020 RCX: ffffa8d64225bb5e RDX: ffff93151d921880 RSI: ffffa8d64225bac8 RDI: ffff931511a1a9d8 RBP: ffffa8d64225bb10 R08: 0000000000000001 R09: ffffa8d64225ba60 R10: 0000000000000002 R11: 000000000000000d R12: 0000000000000001 R13: 0000000000000000 R14: ffffa8d64225bb5e R15: ffff931511a1a9d8 FS: 00007ff8ea7fa9c0(0000) GS:ffff9317fe6c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 000000010d5a4000 CR4: 0000000000750ee0 PKRU: 55555554 Call Trace: drm_dp_dpcd_access+0x72/0x110 [drm_kms_helper] drm_dp_dpcd_read+0xb7/0xf0 [drm_kms_helper] drm_dp_start_crc+0x38/0xb0 [drm_kms_helper] amdgpu_dm_crtc_set_crc_source+0x1ae/0x3e0 [amdgpu] crtc_crc_open+0x174/0x220 [drm] full_proxy_open+0x168/0x1f0 ? open_proxy_open+0x100/0x100 do_dentry_open+0x156/0x370 vfs_open+0x2d/0x30

v2: fix some typo

Signed-off-by: Perry Yuan Perry.Yuan@amd.com --- drivers/gpu/drm/drm_dp_helper.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 6d0f2c447f3b..76b28396001a 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -260,6 +260,10 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, msg.buffer = buffer; msg.size = size;

+ /* No transfer function is set, so not an available DP connector */ + if (!aux->transfer) + return -EINVAL; + mutex_lock(&aux->hw_mutex);

/*