[syzbot] [fs?] general protection fault in configfs_symlink

[syzbot <syzbot+fb804e639c963f8eea9c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2f1baf1fc892 Merge tag 'trace-v7.2-rc7' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1545f149580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=158601bb8cb292dd
dashboard link: https://syzkaller.appspot.com/bug?extid=fb804e639c963f8eea9c
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8dd1ca52ce7b/disk-2f1baf1f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8fdd3c891266/vmlinux-2f1baf1f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c83197355e17/bzImage-2f1baf1f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fb804e639c963f8eea9c@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000016: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000000b0-0x00000000000000b7]
CPU: 1 UID: 0 PID: 8680 Comm: syz.3.808 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:create_link fs/configfs/symlink.c:81 [inline]
RIP: 0010:configfs_symlink+0x5fc/0x1030 fs/configfs/symlink.c:199
Code: 03 42 80 3c 20 00 74 08 48 89 df e8 ae a3 c2 ff 41 bc b0 00 00 00 4c 03 23 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 e7 e8 86 a3 c2 ff 4d 8b 2c 24 4c 89 ef e8
RSP: 0018:ffffc90006b27c80 EFLAGS: 00010202
RAX: 0000000000000016 RBX: ffff88805b9a9a48 RCX: dffffc0000000000
RDX: 0000000000000006 RSI: ffffffff8d881af0 RDI: 00000000ffffffff
RBP: ffffc90006b27d88 R08: ffffffff8faf4f37 R09: 1ffffffff1f5e9e6
R10: dffffc0000000000 R11: fffffbfff1f5e9e7 R12: 00000000000000b0
R13: 0000000000000000 R14: ffffffff8c21fe48 R15: 1ffff92000d64fa0
FS:  00007f70373346c0(0000) GS:ffff888125d45000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff9610f56c8 CR3: 000000005e8fe000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 vfs_symlink+0x18b/0x330 fs/namei.c:5660
 filename_symlinkat+0x1cd/0x420 fs/namei.c:5685
 __do_sys_symlinkat fs/namei.c:5705 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5700
 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: 0033:0x7f703911e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7037334028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f70393a6180 RCX: 00007f703911e0d9
RDX: 0000200000001c00 RSI: ffffffffffffff9c RDI: 0000200000001b00
RBP: 00007f70391b5024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f70393a6218 R14: 00007f70393a6180 R15: 00007ffd2a6d2ad8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:create_link fs/configfs/symlink.c:81 [inline]
RIP: 0010:configfs_symlink+0x5fc/0x1030 fs/configfs/symlink.c:199
Code: 03 42 80 3c 20 00 74 08 48 89 df e8 ae a3 c2 ff 41 bc b0 00 00 00 4c 03 23 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 e7 e8 86 a3 c2 ff 4d 8b 2c 24 4c 89 ef e8
RSP: 0018:ffffc90006b27c80 EFLAGS: 00010202
RAX: 0000000000000016 RBX: ffff88805b9a9a48 RCX: dffffc0000000000
RDX: 0000000000000006 RSI: ffffffff8d881af0 RDI: 00000000ffffffff
RBP: ffffc90006b27d88 R08: ffffffff8faf4f37 R09: 1ffffffff1f5e9e6
R10: dffffc0000000000 R11: fffffbfff1f5e9e7 R12: 00000000000000b0
R13: 0000000000000000 R14: ffffffff8c21fe48 R15: 1ffff92000d64fa0
FS:  00007f70373346c0(0000) GS:ffff888125d45000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3f0968 CR3: 000000005e8fe000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	03 42 80             	add    -0x80(%rdx),%eax
   3:	3c 20                	cmp    $0x20,%al
   5:	00 74 08 48          	add    %dh,0x48(%rax,%rcx,1)
   9:	89 df                	mov    %ebx,%edi
   b:	e8 ae a3 c2 ff       	call   0xffc2a3be
  10:	41 bc b0 00 00 00    	mov    $0xb0,%r12d
  16:	4c 03 23             	add    (%rbx),%r12
  19:	4c 89 e0             	mov    %r12,%rax
  1c:	48 c1 e8 03          	shr    $0x3,%rax
  20:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
  27:	fc ff df
* 2a:	80 3c 08 00          	cmpb   $0x0,(%rax,%rcx,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 e7             	mov    %r12,%rdi
  33:	e8 86 a3 c2 ff       	call   0xffc2a3be
  38:	4d 8b 2c 24          	mov    (%r12),%r13
  3c:	4c 89 ef             	mov    %r13,%rdi
  3f:	e8                   	.byte 0xe8


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