NULL pointer dereference in nv50_disp_chan_mthd() in nouveau driver

Issue

• Kernel panic occurred due to the following messages.

[10088.085129] nouveau 0000:b3:00.0: disp: chid 73 stat 00001080 reason 1 [PUSHBUFFER_ERR] mthd 0200 data badf5040 code badf5040
[10088.085137] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[10088.085139] PGD 0 P4D 0
[10088.085141] Oops: 0000 [#1] SMP NOPTI
[10088.085143] CPU: 11 PID: 0 Comm: swapper/11 Kdump: loaded Tainted: G           OE    --------- -  - 4.18.0-147.el8.x86_64 #1
[10088.085144] Hardware name: Default string Default string/ASMB-815T2-00A1E, BIOS 5.14 03/25/2021
[10088.085184] RIP: 0010:nv50_disp_chan_mthd+0x3e/0x310 [nouveau]
[10088.085186] Code: 8b 77 10 48 89 7c 24 30 89 74 24 1c 65 48 8b 14 25 28 00 00 00 48 89 54 24 70 31 d2 41 39 76 50 0f 82 b0 02 00 00 48 8b 47 08 <4c> 8b 68 20 48 89 44 24 08 4d 85 ed 0f 84 9a 02 00 00 c7 44 24 3c
[10088.085187] RSP: 0018:ffff8b9f7fcc3d48 EFLAGS: 00010002
[10088.085188] RAX: 0000000000000000 RBX: 00000000badf5040 RCX: 0000000000000000
[10088.085189] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8b9f7c7e3b00
[10088.085190] RBP: 000000000061138c R08: 00000000000004f4 R09: 0000000000000004
[10088.085191] R10: 0000000000000049 R11: ffffffff89039b2d R12: ffff8b9f7553d800
[10088.085192] R13: 0000000000000001 R14: ffff8b9f7827d000 R15: ffff8b9f7827d000
[10088.085193] FS:  0000000000000000(0000) GS:ffff8b9f7fcc0000(0000) knlGS:0000000000000000
[10088.085194] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[10088.085194] CR2: 0000000000000020 CR3: 000000099780a005 CR4: 00000000007606e0
[10088.085195] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[10088.085196] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[10088.085197] PKRU: 55555554
[10088.085198] Call Trace:
[10088.085200]  <IRQ>
[10088.085220]  ? nvkm_notify_send+0xf1/0x120 [nouveau]
[10088.085247]  gv100_disp_exception+0x138/0x140 [nouveau]
[10088.085274]  gv100_disp_intr+0x570/0x620 [nouveau]
[10088.085297]  nvkm_mc_intr+0xeb/0x180 [nouveau]
[10088.085321]  nvkm_pci_intr+0x4c/0x90 [nouveau]
[10088.085325]  __handle_irq_event_percpu+0x40/0x180
[10088.085328]  handle_irq_event_percpu+0x30/0x80
[10088.085330]  handle_irq_event+0x36/0x53
[10088.085332]  handle_edge_irq+0x82/0x190
[10088.085334]  handle_irq+0xbf/0x100
[10088.085337]  do_IRQ+0x49/0xd0
[10088.085339]  common_interrupt+0xf/0xf
[10088.085341]  </IRQ>
[10088.085344] RIP: 0010:cpuidle_enter_state+0xb7/0x2a0
[10088.085345] Code: e8 0e 6f a5 ff 80 7c 24 03 00 74 17 9c 58 0f 1f 44 00 00 f6 c4 02 0f 85 d7 01 00 00 31 ff e8 f0 5d ab ff fb 66 0f 1f 44 00 00 <48> b8 ff ff ff ff f3 01 00 00 4c 29 f3 ba ff ff ff 7f 48 39 c3 7f
[10088.085346] RSP: 0018:ffff9dde86717e98 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffd9
[10088.085347] RAX: ffff8b9f7fce3100 RBX: 0000092cd0bae33d RCX: 000000000000001f
[10088.085348] RDX: 0000092cd0bae33d RSI: 000000003351fed6 RDI: 0000000000000000
[10088.085349] RBP: 0000000000000003 R08: 0000000000000004 R09: 0000000000022940
[10088.085350] R10: 00240ecf6caeaaae R11: ffff8b9f7fce20a8 R12: ffff8b9f7fceda50
[10088.085351] R13: ffffffff889254f8 R14: 0000092cd0bac939 R15: 0000000000000000
[10088.085353]  ? cpuidle_enter_state+0x92/0x2a0
[10088.085356]  do_idle+0x236/0x280
[10088.085358]  cpu_startup_entry+0x6f/0x80
[10088.085362]  start_secondary+0x1a7/0x200
[10088.085364]  secondary_startup_64+0xb7/0xc0