[moderation] [fbdev?] general protection fault in fbcon_new_modelist (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d7b8f8e20813 Linux 6.16-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16375f70580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c963f5de3d9eab7d
dashboard link: https://syzkaller.appspot.com/bug?extid=42525d636f430fd5d983
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
CC: [del...@gmx.de dri-...@lists.freedesktop.org linux...@vger.kernel.org linux-...@vger.kernel.org sim...@ffwll.ch]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b35e485ae779/disk-d7b8f8e2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8478fc45f5f6/vmlinux-d7b8f8e2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/86a991e3c539/bzImage-d7b8f8e2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+42525d...@syzkaller.appspotmail.com

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


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.