syzbot


general protection fault in fbcon_new_modelist (2)

Status: moderation: reported on 2025/07/12 03:45
Subsystems: fbdev
[Documentation on labels]
Reported-by: syzbot+42525d636f430fd5d983@syzkaller.appspotmail.com
First crash: 10d, last: 10d
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in fbcon_new_modelist fbdev 2 1 163d 159d 0/29 auto-obsoleted due to no activity on 2025/05/05 22:38

Sample crash report:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000078: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000003c0-0x00000000000003c7]
CPU: 0 UID: 0 PID: 6652 Comm: syz.0.135 Not tainted 6.16.0-rc5-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:fbcon_new_modelist+0x1d2/0x2f0 drivers/video/fbdev/core/fbcon.c:3063
Code: 48 8b 3c d5 d0 ce 09 9b e8 6b 1f fe ff 4c 89 ef 48 89 c6 e8 40 13 fe ff 48 8b 04 24 48 8d b8 c0 03 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 74 08 3c 01 0f 8e bf 00 00 00 48 8b 04 24 4c
RSP: 0000:ffffc9001a237870 EFLAGS: 00010206
RAX: 0000000000000078 RBX: 0000000000000015 RCX: ffffc9000d23d000
RDX: 0000000000000000 RSI: ffffffff8520eba3 RDI: 00000000000003c0
RBP: ffff888142368000 R08: 0000000000000004 R09: 00000000000006e0
R10: 00000000ffffffff R11: 0000000000000001 R12: dffffc0000000000
R13: ffffc9001a2378a8 R14: ffffffff9b09d8a8 R15: 0000000000000015
FS:  00007f3c795386c0(0000) GS:ffff888124723000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000001d2000 CR3: 0000000012c56000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 fb_new_modelist+0x331/0x450 drivers/video/fbdev/core/fbmem.c:733
 store_modes+0x1c8/0x3e0 drivers/video/fbdev/core/fbsysfs.c:113
 dev_attr_store+0x58/0x80 drivers/base/core.c:2440
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x6c4/0x1150 fs/read_write.c:686
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3c7878e929
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:00007f3c79538038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3c789b6160 RCX: 00007f3c7878e929
RDX: 000000000000ffd8 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f3c78810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f3c789b6160 R15: 00007fff22ee2708
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fbcon_new_modelist+0x1d2/0x2f0 drivers/video/fbdev/core/fbcon.c:3063
Code: 48 8b 3c d5 d0 ce 09 9b e8 6b 1f fe ff 4c 89 ef 48 89 c6 e8 40 13 fe ff 48 8b 04 24 48 8d b8 c0 03 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 74 08 3c 01 0f 8e bf 00 00 00 48 8b 04 24 4c
RSP: 0000:ffffc9001a237870 EFLAGS: 00010206
RAX: 0000000000000078 RBX: 0000000000000015 RCX: ffffc9000d23d000
RDX: 0000000000000000 RSI: ffffffff8520eba3 RDI: 00000000000003c0
RBP: ffff888142368000 R08: 0000000000000004 R09: 00000000000006e0
R10: 00000000ffffffff R11: 0000000000000001 R12: dffffc0000000000
R13: ffffc9001a2378a8 R14: ffffffff9b09d8a8 R15: 0000000000000015
FS:  00007f3c795386c0(0000) GS:ffff888124723000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000001d2000 CR3: 0000000012c56000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	48 8b 3c d5 d0 ce 09 	mov    -0x64f63130(,%rdx,8),%rdi
   7:	9b
   8:	e8 6b 1f fe ff       	call   0xfffe1f78
   d:	4c 89 ef             	mov    %r13,%rdi
  10:	48 89 c6             	mov    %rax,%rsi
  13:	e8 40 13 fe ff       	call   0xfffe1358
  18:	48 8b 04 24          	mov    (%rsp),%rax
  1c:	48 8d b8 c0 03 00 00 	lea    0x3c0(%rax),%rdi
  23:	48 89 f8             	mov    %rdi,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	74 08                	je     0x3b
  33:	3c 01                	cmp    $0x1,%al
  35:	0f 8e bf 00 00 00    	jle    0xfa
  3b:	48 8b 04 24          	mov    (%rsp),%rax
  3f:	4c                   	rex.WR

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/08 03:40 upstream d7b8f8e20813 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto general protection fault in fbcon_new_modelist
* Struck through repros no longer work on HEAD.