[syzbot] [afs?] general protection fault in afs_request_key

[syzbot <syzbot+41c68824eefb67cdf00c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2eba5e05d9bc Merge tag 'loongarch-fixes-6.18-2' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15ad5a12580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f
dashboard link: https://syzkaller.appspot.com/bug?extid=41c68824eefb67cdf00c
compiler:       gcc (Debian 12.2.0-14+deb12u1) 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/86850e631d99/disk-2eba5e05.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0a4e0560b906/vmlinux-2eba5e05.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3ff9e4ed22aa/bzImage-2eba5e05.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+41c68824eefb67cdf00c@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000024: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000120-0x0000000000000127]
CPU: 0 UID: 0 PID: 8382 Comm: syz.3.612 Tainted: G     U              syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:afs_request_key+0xba/0x190 fs/afs/security.c:30
Code: 48 c1 e9 03 80 3c 01 00 0f 85 ae 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 30 48 8d bd 20 01 00 00 48 89 f9 48 c1 e9 03 <80> 3c 01 00 75 7a 48 8b b5 20 01 00 00 31 c9 48 c7 c7 80 59 41 90
RSP: 0018:ffffc90004a7fc88 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888025b53000 RCX: 0000000000000024
RDX: ffff8880315b88c0 RSI: ffffffff83963434 RDI: 0000000000000120
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888025b53030
R13: ffff88802b8e6320 R14: ffffed100571cc66 R15: ffffc90004a7fea0
FS:  00007efe225c96c0(0000) GS:ffff888124a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30fbcff8 CR3: 0000000060a84000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 afs_validate_fc fs/afs/super.c:376 [inline]
 afs_get_tree+0x303/0x1380 fs/afs/super.c:555
 vfs_get_tree+0x8e/0x340 fs/super.c:1758
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3642 [inline]
 do_new_mount fs/namespace.c:3718 [inline]
 path_mount+0x7b9/0x23a0 fs/namespace.c:4028
 do_mount fs/namespace.c:4041 [inline]
 __do_sys_mount fs/namespace.c:4229 [inline]
 __se_sys_mount fs/namespace.c:4206 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4206
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efe2178f749
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:00007efe225c9038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007efe219e5fa0 RCX: 00007efe2178f749
RDX: 00002000000001c0 RSI: 0000200000000180 RDI: 0000000000000000
RBP: 00007efe21813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efe219e6038 R14: 00007efe219e5fa0 R15: 00007ffdcf161ca8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:afs_request_key+0xba/0x190 fs/afs/security.c:30
Code: 48 c1 e9 03 80 3c 01 00 0f 85 ae 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 30 48 8d bd 20 01 00 00 48 89 f9 48 c1 e9 03 <80> 3c 01 00 75 7a 48 8b b5 20 01 00 00 31 c9 48 c7 c7 80 59 41 90
RSP: 0018:ffffc90004a7fc88 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888025b53000 RCX: 0000000000000024
RDX: ffff8880315b88c0 RSI: ffffffff83963434 RDI: 0000000000000120
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888025b53030
R13: ffff88802b8e6320 R14: ffffed100571cc66 R15: ffffc90004a7fea0
FS:  00007efe225c96c0(0000) GS:ffff888124a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30f03ff8 CR3: 0000000060a84000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	48 c1 e9 03          	shr    $0x3,%rcx
   4:	80 3c 01 00          	cmpb   $0x0,(%rcx,%rax,1)
   8:	0f 85 ae 00 00 00    	jne    0xbc
   e:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  15:	fc ff df
  18:	48 8b 6b 30          	mov    0x30(%rbx),%rbp
  1c:	48 8d bd 20 01 00 00 	lea    0x120(%rbp),%rdi
  23:	48 89 f9             	mov    %rdi,%rcx
  26:	48 c1 e9 03          	shr    $0x3,%rcx
* 2a:	80 3c 01 00          	cmpb   $0x0,(%rcx,%rax,1) <-- trapping instruction
  2e:	75 7a                	jne    0xaa
  30:	48 8b b5 20 01 00 00 	mov    0x120(%rbp),%rsi
  37:	31 c9                	xor    %ecx,%ecx
  39:	48 c7 c7 80 59 41 90 	mov    $0xffffffff90415980,%rdi


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