[v6.6] general protection fault in configfs_symlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c5596480c50e Linux 6.6.145
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=174927b1580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=427f6b79598633b285d8
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/eb5cda0a8020/disk-c5596480.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca05ff2fc502/vmlinux-c5596480.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6daf3255b985/bzImage-c5596480.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+427f6b...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000001e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000f0-0x00000000000000f7]
CPU: 0 PID: 27211 Comm: syz.4.3941 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:create_link fs/configfs/symlink.c:81 [inline]
RIP: 0010:configfs_symlink+0x5fd/0xfe0 fs/configfs/symlink.c:205
Code: 48 83 c3 48 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 f3 50 c8 ff 41 be f0 00 00 00 4c 03 33 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 d4 50 c8 ff 4d 8b 36 4c 89 f7 e8
RSP: 0018:ffffc9000b9bfce0 EFLAGS: 00010206
RAX: 000000000000001e RBX: ffff88806a3f7948 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b1d0640 RDI: 00000000ffffffff
RBP: ffffc9000b9bfdf0 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 0000000000000000
R13: dffffc0000000000 R14: 00000000000000f0 R15: ffff88807860e000
FS: 00007fc4ac1386c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc4ac137ff8 CR3: 0000000064ac4000 CR4: 00000000003506f0
Call Trace:
<TASK>
vfs_symlink+0x138/0x2b0 fs/namei.c:4485
do_symlinkat+0x1ba/0x400 fs/namei.c:4511
__do_sys_symlinkat fs/namei.c:4527 [inline]
__se_sys_symlinkat fs/namei.c:4524 [inline]
__x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4524
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc4ab19de99
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:00007fc4ac138028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007fc4ab426090 RCX: 00007fc4ab19de99
RDX: 0000200000000500 RSI: ffffffffffffff9c RDI: 0000200000000400
RBP: 00007fc4ab233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc4ab426128 R14: 00007fc4ab426090 R15: 00007ffd61648af8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:create_link fs/configfs/symlink.c:81 [inline]
RIP: 0010:configfs_symlink+0x5fd/0xfe0 fs/configfs/symlink.c:205
Code: 48 83 c3 48 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 f3 50 c8 ff 41 be f0 00 00 00 4c 03 33 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 d4 50 c8 ff 4d 8b 36 4c 89 f7 e8
RSP: 0018:ffffc9000b9bfce0 EFLAGS: 00010206
RAX: 000000000000001e RBX: ffff88806a3f7948 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b1d0640 RDI: 00000000ffffffff
RBP: ffffc9000b9bfdf0 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 0000000000000000
R13: dffffc0000000000 R14: 00000000000000f0 R15: ffff88807860e000
FS: 00007fc4ac1386c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055557c22aa38 CR3: 0000000064ac4000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
0: 48 83 c3 48 add $0x48,%rbx
4: 48 89 d8 mov %rbx,%rax
7: 48 c1 e8 03 shr $0x3,%rax
b: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
10: 74 08 je 0x1a
12: 48 89 df mov %rbx,%rdi
15: e8 f3 50 c8 ff call 0xffc8510d
1a: 41 be f0 00 00 00 mov $0xf0,%r14d
20: 4c 03 33 add (%rbx),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 f7 mov %r14,%rdi
34: e8 d4 50 c8 ff call 0xffc8510d
39: 4d 8b 36 mov (%r14),%r14
3c: 4c 89 f7 mov %r14,%rdi
3f: e8 .byte 0xe8


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