syzbot
general protection fault in __drm_fb_helper_restore_fbdev_mode_unlocked
Status:
moderation: reported on 2026/09/08 13:16
Subsystems:
dri
Labels:
prio:high
[Documentation on labels]
Reported-by: syzbot+36ab87bab36035e90310@syzkaller.appspotmail.com
First crash: 4d01h, last: 1d04h
Sample crash report:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 UID: 0 PID: 18216 Comm: syz.0.2949 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__drm_fb_helper_restore_fbdev_mode_unlocked+0x124/0x1c0 drivers/gpu/drm/drm_fb_helper.c:149
Code: 8d b3 e0 00 00 00 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 fa 36 97 fc 4d 8b 36 49 83 c6 08 4c 89 f0 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 f7 e8 dd 36 97 fc 4d 8b 36 4d 85 f6 74
RSP: 0018:ffffc90004bc7c60 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff888026e83800 RCX: 1ffff92000978f74
RDX: 0000000000000001 RSI: 0000000000000008 RDI: 00000000ffffffff
RBP: 00000000fffffff0 R08: ffffc90004bc7be7 R09: 1ffff92000978f7c
R10: dffffc0000000000 R11: fffff52000978f7d R12: dffffc0000000000
R13: 1ffff11004dd0753 R14: 0000000000000008 R15: ffff888026e83a98
FS: 000055556d227500(0000) GS:ffff888124dd9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c36982d CR3: 000000002bc80000 CR4: 00000000003526f0
Call Trace:
<TASK>
drm_fbdev_client_restore+0x1b/0x30 drivers/gpu/drm/clients/drm_fbdev_client.c:45
drm_client_dev_restore+0x14c/0x290 drivers/gpu/drm/drm_client_event.c:118
drm_lastclose drivers/gpu/drm/drm_file.c:408 [inline]
drm_release+0x32d/0x400 drivers/gpu/drm/drm_file.c:441
__fput+0x418/0xa50 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc35cb9e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc35cf4fba8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fc35cf4fc90 RCX: 00007fc35cb9e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000b4dd0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32420000 R11: 0000000000000246 R12: 00007fc35cf4fcd0
R13: 00007fc35ce25fac R14: 00000000000b5471 R15: 00007fc35ce25fa0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__drm_fb_helper_restore_fbdev_mode_unlocked+0x124/0x1c0 drivers/gpu/drm/drm_fb_helper.c:149
Code: 8d b3 e0 00 00 00 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 fa 36 97 fc 4d 8b 36 49 83 c6 08 4c 89 f0 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 f7 e8 dd 36 97 fc 4d 8b 36 4d 85 f6 74
RSP: 0018:ffffc90004bc7c60 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff888026e83800 RCX: 1ffff92000978f74
RDX: 0000000000000001 RSI: 0000000000000008 RDI: 00000000ffffffff
RBP: 00000000fffffff0 R08: ffffc90004bc7be7 R09: 1ffff92000978f7c
R10: dffffc0000000000 R11: fffff52000978f7d R12: dffffc0000000000
R13: 1ffff11004dd0753 R14: 0000000000000008 R15: ffff888026e83a98
FS: 000055556d227500(0000) GS:ffff888124dd9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f10135ef2f8 CR3: 000000002bc80000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 8d b3 e0 00 00 00 lea 0xe0(%rbx),%esi
6: 4c 89 f0 mov %r14,%rax
9: 48 c1 e8 03 shr $0x3,%rax
d: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
12: 74 08 je 0x1c
14: 4c 89 f7 mov %r14,%rdi
17: e8 fa 36 97 fc call 0xfc973716
1c: 4d 8b 36 mov (%r14),%r14
1f: 49 83 c6 08 add $0x8,%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 f7 mov %r14,%rdi
34: e8 dd 36 97 fc call 0xfc973716
39: 4d 8b 36 mov (%r14),%r14
3c: 4d 85 f6 test %r14,%r14
3f: 74 .byte 0x74
* Struck through repros no longer work on HEAD.