linux-kernel - [syzbot] [fbdev?] UBSAN: array-index-out-of-bounds in fbcon_info_from

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Message-ID: <679d0a8f.050a0220.163cdc.000c.GAE@google.com>
Date: Fri, 31 Jan 2025 09:38:23 -0800
From: syzbot <syzbot+a7d4444e7b6e743572f7@...kaller.appspotmail.com>
To: deller@....de, dri-devel@...ts.freedesktop.org, 
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org, simona@...ll.ch, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [fbdev?] UBSAN: array-index-out-of-bounds in fbcon_info_from_console

Hello,

syzbot found the following issue on:

HEAD commit:    9c5968db9e62 Merge tag 'mm-stable-2025-01-26-14-59' of git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15045118580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e0b04511e541daf8
dashboard link: https://syzkaller.appspot.com/bug?extid=a7d4444e7b6e743572f7
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/28361a445db1/disk-9c5968db.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3341d04d577f/vmlinux-9c5968db.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e5b54cd0e552/bzImage-9c5968db.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a7d4444e7b6e743572f7@...kaller.appspotmail.com

netlink: zone id is out of range
netlink: zone id is out of range
netlink: zone id is out of range
netlink: zone id is out of range
netlink: zone id is out of range
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in drivers/video/fbdev/core/fbcon.c:122:28
index -1 is out of range for type 'fb_info *[32]'
CPU: 1 UID: 0 PID: 8491 Comm: syz.4.565 Not tainted 6.13.0-syzkaller-08265-g9c5968db9e62 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_out_of_bounds+0x110/0x150 lib/ubsan.c:429
 fbcon_info_from_console+0x192/0x1a0 drivers/video/fbdev/core/fbcon.c:122
 fbcon_new_modelist+0xbf/0x2d0 drivers/video/fbdev/core/fbcon.c:3048
 fb_new_modelist+0x328/0x440 drivers/video/fbdev/core/fbmem.c:673
 store_modes+0x1c9/0x3e0 drivers/video/fbdev/core/fbsysfs.c:113
 dev_attr_store+0x55/0x80 drivers/base/core.c:2439
 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
 kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:679
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe6d0f8cd29
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:00007fe6d1daa038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fe6d11a5fa0 RCX: 00007fe6d0f8cd29
RDX: 000000000000a3d9 RSI: 0000000020000400 RDI: 0000000000000009
RBP: 00007fe6d100e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe6d11a5fa0 R15: 00007ffe594083d8
 </TASK>
---[ end trace ]---


---
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