[syzbot] [linux1394?] general protection fault in ar_context_release

[syzbot <syzbot+d30aad27833a559defab@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    848acc8ffe1b Merge tag 'fsverity-for-linus' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11f46cc6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4e38b15c29e6a1d9
dashboard link: https://syzkaller.appspot.com/bug?extid=d30aad27833a559defab
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15837649580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11a693b9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9bf3ffd710de/disk-848acc8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/770c0a63a80c/vmlinux-848acc8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c54f9393cb03/bzImage-848acc8f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d30aad27833a559defab@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 UID: 0 PID: 5635 Comm: syz-executor890 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:ar_context_release+0x3f/0x380 drivers/firewire/ohci.c:543
Code: ff df e8 04 56 74 fa 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 0f ef e1 fa 4c 8b 33 49 83 c6 08 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 f3 ee e1 fa 4d 8b 3e 4c 8d 63 48 4d
RSP: 0018:ffffc90003707a30 EFLAGS: 00010212
RAX: 0000000000000001 RBX: ffff88803580c9c0 RCX: ffff88807f550000
RDX: 0000000000000000 RSI: ffff88803580c038 RDI: ffff88803580c9c0
RBP: dffffc0000000000 R08: ffffffff90579d37 R09: 1ffffffff20af3a6
R10: dffffc0000000000 R11: ffffffff812dfe10 R12: ffff88803580c000
R13: dffffc0000000000 R14: 0000000000000008 R15: ffffc90003707ac0
FS:  000055558e6e2400(0000) GS:ffff88812504b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562371f1a150 CR3: 000000007b54d000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 release_ohci+0x3f/0x60 drivers/firewire/ohci.c:3567
 release_nodes drivers/base/devres.c:546 [inline]
 devres_release_all+0x1a8/0x260 drivers/base/devres.c:576
 device_unbind_cleanup drivers/base/dd.c:597 [inline]
 really_probe+0x451/0xae0 drivers/base/dd.c:772
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 device_driver_attach+0xe0/0x1d0 drivers/base/dd.c:1203
 bind_store+0x1d0/0x220 drivers/base/bus.c:267
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdb76e15649
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcdb4998a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000200000000000 RCX: 00007fdb76e15649
RDX: 000000000000000d RSI: 0000200000000180 RDI: 0000000000000005
RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffcdb499a18
R13: 0000200000000004 R14: 00007fdb76ea8c40 R15: 0000000000000002
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
R13: dffffc0000000000 R14: 0000000000000008 R15: ffffc90003707ac0
FS:  000055558e6e2400(0000) GS:ffff888124f4b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc34a7f2708 CR3: 000000007b54d000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	ff                   	lcall  (bad)
   1:	df e8                	fucomip %st(0),%st
   3:	04 56                	add    $0x56,%al
   5:	74 fa                	je     0x1
   7:	48 89 d8             	mov    %rbx,%rax
   a:	48 c1 e8 03          	shr    $0x3,%rax
   e:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
  12:	74 08                	je     0x1c
  14:	48 89 df             	mov    %rbx,%rdi
  17:	e8 0f ef e1 fa       	call   0xfae1ef2b
  1c:	4c 8b 33             	mov    (%rbx),%r14
  1f:	49 83 c6 08          	add    $0x8,%r14
  23:	4c 89 f0             	mov    %r14,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 f7             	mov    %r14,%rdi
  33:	e8 f3 ee e1 fa       	call   0xfae1ef2b
  38:	4d 8b 3e             	mov    (%r14),%r15
  3b:	4c 8d 63 48          	lea    0x48(%rbx),%r12
  3f:	4d                   	rex.WRB


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