syzbot


divide error in drm_mode_debug_printmodeline

Status: upstream: reported C repro on 2023/09/15 11:23
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+ea0ff9cfb920e6638412@syzkaller.appspotmail.com
First crash: 277d, last: 16d
Bug presence (1)
Date Name Commit Repro Result
2023/09/15 upstream (ToT) 9fdfb15a3dbf C [report] divide error in drm_mode_debug_printmodeline
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream divide error in drm_mode_debug_printmodeline dri C done 4 54d 216d 0/27 upstream: reported C repro on 2023/11/15 09:34
linux-5.15 divide error in drm_mode_debug_printmodeline origin:upstream C 1 7d22h 326d 0/3 upstream: reported C repro on 2023/07/28 20:01
Fix bisection attempts (8)
Created Duration User Patch Repo Result
2024/06/02 06:57 1h06m bisect fix linux-6.1.y job log (0) log
2024/05/01 03:12 1h22m bisect fix linux-6.1.y job log (0) log
2024/03/31 15:52 1h23m bisect fix linux-6.1.y job log (0) log
2024/03/01 07:19 1h11m bisect fix linux-6.1.y job log (0) log
2024/01/21 18:16 1h23m bisect fix linux-6.1.y job log (0) log
2023/12/22 15:52 1h28m bisect fix linux-6.1.y job log (0) log
2023/11/22 09:38 1h16m bisect fix linux-6.1.y job log (0) log
2023/10/19 07:31 1h03m bisect fix linux-6.1.y job log (0) log

Sample crash report:
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 3542 Comm: syz-executor350 Not tainted 6.1.53-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
RIP: 0010:drm_mode_vrefresh drivers/gpu/drm/drm_modes.c:826 [inline]
RIP: 0010:drm_mode_debug_printmodeline+0x114/0x4e0 drivers/gpu/drm/drm_modes.c:59
Code: 00 41 0f b7 07 66 83 f8 02 b9 01 00 00 00 0f 43 c8 0f b7 c1 0f af e8 44 89 f0 48 69 c8 e8 03 00 00 89 e8 d1 e8 48 01 c8 31 d2 <48> f7 f5 49 89 c6 eb 0c e8 af a0 cb fc eb 05 e8 a8 a0 cb fc 48 89
RSP: 0018:ffffc900039df8f0 EFLAGS: 00010246
RAX: 000000000001f400 RBX: ffff888022a3ec00 RCX: 000000000001f400
RDX: 0000000000000000 RSI: 0000000000008000 RDI: ffff888022a3ec18
RBP: 0000000000000000 R08: ffffffff84be72db R09: ffffc900039df8c0
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000080
R13: dffffc0000000000 R14: 0000000000000080 R15: ffff888022a3ec16
FS:  0000555557523380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 0000000072740000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 drm_mode_setcrtc+0x837/0x1870 drivers/gpu/drm/drm_crtc.c:794
 drm_ioctl_kernel+0x345/0x4f0 drivers/gpu/drm/drm_ioctl.c:788
 drm_ioctl+0x618/0x9f0 drivers/gpu/drm/drm_ioctl.c:891
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7670638729
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdec685298 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffdec685468 RCX: 00007f7670638729
RDX: 0000000020000180 RSI: 00000000c06864a2 RDI: 0000000000000003
RBP: 00007f76706ab610 R08: 00000000fffff4e6 R09: 00007ffdec685468
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffdec685458 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:drm_mode_vrefresh drivers/gpu/drm/drm_modes.c:826 [inline]
RIP: 0010:drm_mode_debug_printmodeline+0x114/0x4e0 drivers/gpu/drm/drm_modes.c:59
Code: 00 41 0f b7 07 66 83 f8 02 b9 01 00 00 00 0f 43 c8 0f b7 c1 0f af e8 44 89 f0 48 69 c8 e8 03 00 00 89 e8 d1 e8 48 01 c8 31 d2 <48> f7 f5 49 89 c6 eb 0c e8 af a0 cb fc eb 05 e8 a8 a0 cb fc 48 89
RSP: 0018:ffffc900039df8f0 EFLAGS: 00010246
RAX: 000000000001f400 RBX: ffff888022a3ec00 RCX: 000000000001f400
RDX: 0000000000000000 RSI: 0000000000008000 RDI: ffff888022a3ec18
RBP: 0000000000000000 R08: ffffffff84be72db R09: ffffc900039df8c0
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000080
R13: dffffc0000000000 R14: 0000000000000080 R15: ffff888022a3ec16
FS:  0000555557523380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 0000000072740000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	00 41 0f             	add    %al,0xf(%rcx)
   3:	b7 07                	mov    $0x7,%bh
   5:	66 83 f8 02          	cmp    $0x2,%ax
   9:	b9 01 00 00 00       	mov    $0x1,%ecx
   e:	0f 43 c8             	cmovae %eax,%ecx
  11:	0f b7 c1             	movzwl %cx,%eax
  14:	0f af e8             	imul   %eax,%ebp
  17:	44 89 f0             	mov    %r14d,%eax
  1a:	48 69 c8 e8 03 00 00 	imul   $0x3e8,%rax,%rcx
  21:	89 e8                	mov    %ebp,%eax
  23:	d1 e8                	shr    %eax
  25:	48 01 c8             	add    %rcx,%rax
  28:	31 d2                	xor    %edx,%edx
* 2a:	48 f7 f5             	div    %rbp <-- trapping instruction
  2d:	49 89 c6             	mov    %rax,%r14
  30:	eb 0c                	jmp    0x3e
  32:	e8 af a0 cb fc       	call   0xfccba0e6
  37:	eb 05                	jmp    0x3e
  39:	e8 a8 a0 cb fc       	call   0xfccba0e6
  3e:	48                   	rex.W
  3f:	89                   	.byte 0x89

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/09/15 11:21 linux-6.1.y 09045dae0d90 0b6a67ac .config console log report syz C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan divide error in drm_mode_debug_printmodeline
* Struck through repros no longer work on HEAD.