syzbot


general protection fault in fb_videomode_to_var

Status: moderation: reported on 2024/12/16 08:12
Subsystems: fbdev
[Documentation on labels]
Reported-by: syzbot+bf6dae7641af87503402@syzkaller.appspotmail.com
First crash: 155d, last: 12d
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel paging request in fb_videomode_to_var fbdev 1 307d 303d 0/28 auto-obsoleted due to no activity on 2024/10/11 19:33
linux-5.15 BUG: unable to handle kernel paging request in fb_videomode_to_var origin:upstream C 2 3d07h 17d 0/3 upstream: reported C repro on 2025/04/29 08:31

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: 7250 Comm: syz.0.377 Not tainted 6.15.0-rc4-syzkaller-00291-g2a239ffbebb5 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
RIP: 0010:fb_videomode_to_var+0x2e/0x600 drivers/video/fbdev/core/modedb.c:905
Code: 55 41 57 41 56 41 55 41 54 53 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 ed f7 c2 fc 4d 8d 7e 0c 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 c7 02 00 00 41 8b 2f 48 89 d8 48 c1 e8
RSP: 0018:ffffc9000b6b7688 EFLAGS: 00010203
RAX: 0000000000000001 RBX: ffffc9000b6b7760 RCX: 0000000000080000
RDX: ffffc9000c0d9000 RSI: 0000000000000889 RDI: 000000000000088a
RBP: ffffc9000b6b7890 R08: ffffc9000b6b77ff R09: 0000000000000000
R10: ffffc9000b6b7760 R11: fffff520016d6f00 R12: 0000000000000100
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000000c
FS:  00007ffb8d4876c0(0000) GS:ffff8881261ff000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c28fbde CR3: 0000000033718000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 display_to_var drivers/video/fbdev/core/fbcon.c:923 [inline]
 fbcon_switch+0x55a/0x1fc0 drivers/video/fbdev/core/fbcon.c:2118
 redraw_screen+0x56a/0xe90 drivers/tty/vt/vt.c:957
 vc_do_resize+0x122d/0x1770 drivers/tty/vt/vt.c:1272
 vc_resize include/linux/vt_kern.h:49 [inline]
 fbcon_modechanged+0x70e/0x11b0 drivers/video/fbdev/core/fbcon.c:2680
 do_fb_ioctl+0x6fd/0x750 drivers/video/fbdev/core/fb_chrdev.c:92
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ffb8c58e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffb8d487038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffb8c7b5fa0 RCX: 00007ffb8c58e969
RDX: 0000200000000100 RSI: 0000000000004601 RDI: 000000000000000a
RBP: 00007ffb8c610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffb8c7b5fa0 R15: 00007fff7ad75be8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fb_videomode_to_var+0x2e/0x600 drivers/video/fbdev/core/modedb.c:905
Code: 55 41 57 41 56 41 55 41 54 53 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 ed f7 c2 fc 4d 8d 7e 0c 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 c7 02 00 00 41 8b 2f 48 89 d8 48 c1 e8
RSP: 0018:ffffc9000b6b7688 EFLAGS: 00010203
RAX: 0000000000000001 RBX: ffffc9000b6b7760 RCX: 0000000000080000
RDX: ffffc9000c0d9000 RSI: 0000000000000889 RDI: 000000000000088a
RBP: ffffc9000b6b7890 R08: ffffc9000b6b77ff R09: 0000000000000000
R10: ffffc9000b6b7760 R11: fffff520016d6f00 R12: 0000000000000100
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000000c
FS:  00007ffb8d4876c0(0000) GS:ffff8881261ff000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c28fbde CR3: 0000000033718000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	55                   	push   %rbp
   1:	41 57                	push   %r15
   3:	41 56                	push   %r14
   5:	41 55                	push   %r13
   7:	41 54                	push   %r12
   9:	53                   	push   %rbx
   a:	49 89 f6             	mov    %rsi,%r14
   d:	48 89 fb             	mov    %rdi,%rbx
  10:	49 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%r13
  17:	fc ff df
  1a:	e8 ed f7 c2 fc       	call   0xfcc2f80c
  1f:	4d 8d 7e 0c          	lea    0xc(%r14),%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 28       	movzbl (%rax,%r13,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 c7 02 00 00    	jne    0x2fe
  37:	41 8b 2f             	mov    (%r15),%ebp
  3a:	48 89 d8             	mov    %rbx,%rax
  3d:	48                   	rex.W
  3e:	c1                   	.byte 0xc1
  3f:	e8                   	.byte 0xe8

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/04 10:47 upstream 2a239ffbebb5 b0714e37 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root general protection fault in fb_videomode_to_var
2025/04/03 09:52 upstream 92b71befc349 996a9618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 general protection fault in fb_videomode_to_var
2024/12/12 08:02 upstream 231825b2e1ff ff949d25 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 general protection fault in fb_videomode_to_var
2025/01/29 09:37 upstream 805ba04cb7cc 865ef71e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in fb_videomode_to_var
* Struck through repros no longer work on HEAD.