Laptop dock and undock results in a NULL pointer dereference within drm_dp_get_mst_branch_device()

Solution Verified - Updated -

Issue

  • When docking the workstation, it will sporadically crash, generating a kernel panic.
  • System panics with below call trace:
Hardware name: Dell Inc. Precision 5520/0J1PNH, BIOS 1.11.0 07/24/2018
Workqueue: i915-dp i915_digport_work_func [i915]
task: ffff975056f58000 ti: ffff975056f60000 task.ti: ffff975056f60000
RIP: 0010:[<ffffffffc034ce5e>]  [<ffffffffc034ce5e>] drm_dp_get_mst_branch_device+0xee/0x120 [drm_kms_helper]
RSP: 0018:ffff975056f63c98  EFLAGS: 00010246
RAX: 0000000000000001 RBX: ffff974973ee29a8 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffff975056f58000 RDI: ffff974973ee29ac
RBP: ffff975056f63cb8 R08: ffff975056f60000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff974973ee2850 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff97507e480000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000085c012000 CR4: 00000000003607e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
[<ffffffffc034f116>] drm_dp_mst_hpd_irq+0xc6/0x960 [drm_kms_helper]
[<ffffffffc04c164f>] intel_dp_check_mst_status+0xcf/0x210 [i915]
[<ffffffffc04c8da0>] intel_dp_hpd_pulse+0x190/0x340 [i915]
[<ffffffffc04ac397>] i915_digport_work_func+0xa7/0x130 [i915]
[<ffffffff93cb35ef>] process_one_work+0x17f/0x440
[<ffffffff93cb4686>] worker_thread+0x126/0x3c0
[<ffffffff93cb4560>] ? manage_workers.isra.24+0x2a0/0x2a0
[<ffffffff93cbb621>] kthread+0xd1/0xe0
[<ffffffff93cbb550>] ? insert_kthread_work+0x40/0x40
[<ffffffff943205dd>] ret_from_fork_nospec_begin+0x7/0x21
[<ffffffff93cbb550>] ? insert_kthread_work+0x40/0x40
Code: 20 4d 85 e4 75 d5 45 0f b6 45 00 89 d1 31 f6 48 c7 c2 58 d7 35 c0 48 c7 c7 6d ea 35 c0 31 c0 e8 f9 96 f2 ff eb 13 b8 01 00 00 00 <f0> 41 0f c1 04 24 83 c0 01 83 f8 01 7e 14 48 89 df e8 fc 51 fc 
RIP  [<ffffffffc034ce5e>] drm_dp_get_mst_branch_device+0xee/0x120 [drm_kms_helper]
RSP <ffff975056f63c98>
CR2: 0000000000000000

Environment

  • Red Hat Enterprise Linux 7.5

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