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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 62cc90241548 Merge tag 'mm-hotfixes-stable-2026-07-27-14-1..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=161767b1580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
dashboard link: https://syzkaller.appspot.com/bug?extid=ee5128869a80ee2589f0
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [a.hin...@kernel.org lei...@debian.org linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/727c8b2ee0d6/disk-62cc9024.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4e2cc8ae0237/vmlinux-62cc9024.xz
kernel image: https://storage.googleapis.com/syzbot-assets/beb9a012f168/bzImage-62cc9024.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ee5128...@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: 0 UID: 0 PID: 19942 Comm: syz.3.1037 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
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+0x5fc/0x1030 fs/configfs/symlink.c:199
Code: 03 42 80 3c 20 00 74 08 48 89 df e8 1e e9 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 f6 e8 c2 ff 4d 8b 2c 24 4c 89 ef e8
RSP: 0018:ffffc90004837c80 EFLAGS: 00010202
RAX: 0000000000000016 RBX: ffff88805cf3a648 RCX: dffffc0000000000
RDX: 0000000000000006 RSI: ffffffff8d88567f RDI: 00000000ffffffff
RBP: ffffc90004837d88 R08: ffffffff8faf9737 R09: 1ffffffff1f5f2e6
R10: dffffc0000000000 R11: fffffbfff1f5f2e7 R12: 00000000000000b0
R13: 0000000000000000 R14: ffffffff8c224508 R15: 1ffff92000906fa0
FS: 00007f8e86ee56c0(0000) GS:ffff888125c41000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2df0cff8 CR3: 0000000035d02000 CR4: 00000000003526f0
Call Trace:
<TASK>
vfs_symlink+0x18b/0x330 fs/namei.c:5660
filename_symlinkat+0x1cd/0x420 fs/namei.c:5685
__do_sys_symlink fs/namei.c:5712 [inline]
__se_sys_symlink+0x4d/0x2b0 fs/namei.c:5708
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: 0033:0x7f8e88cade99
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:00007f8e86ee5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f8e88f36090 RCX: 00007f8e88cade99
RDX: 0000000000000000 RSI: 0000200000001900 RDI: 0000200000001800
RBP: 00007f8e88d43eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8e88f36128 R14: 00007f8e88f36090 R15: 00007ffeff1fdf38
</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 1e e9 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 f6 e8 c2 ff 4d 8b 2c 24 4c 89 ef e8
RSP: 0018:ffffc90004837c80 EFLAGS: 00010202
RAX: 0000000000000016 RBX: ffff88805cf3a648 RCX: dffffc0000000000
RDX: 0000000000000006 RSI: ffffffff8d88567f RDI: 00000000ffffffff
RBP: ffffc90004837d88 R08: ffffffff8faf9737 R09: 1ffffffff1f5f2e6
R10: dffffc0000000000 R11: fffffbfff1f5f2e7 R12: 00000000000000b0
R13: 0000000000000000 R14: ffffffff8c224508 R15: 1ffff92000906fa0
FS: 00007f8e86ee56c0(0000) GS:ffff888125c41000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2df0cff8 CR3: 0000000035d02000 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 1e e9 c2 ff call 0xffc2e92e
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 f6 e8 c2 ff call 0xffc2e92e
38: 4d 8b 2c 24 mov (%r12),%r13
3c: 4c 89 ef mov %r13,%rdi
3f: e8 .byte 0xe8


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