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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 785f0eb2f85d Add linux-next specific files for 20260320
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15e61572580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c584910d0d74158d
dashboard link: https://syzkaller.appspot.com/bug?extid=17ad84d4523cd719c6d2
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a1f7fd9c1a63/disk-785f0eb2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c138da87c25/vmlinux-785f0eb2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4d1be64e56db/bzImage-785f0eb2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+17ad84...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN PTI
KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]
CPU: 0 UID: 0 PID: 14965 Comm: syz.7.3353 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__hlist_del include/linux/list.h:992 [inline]
RIP: 0010:hlist_del include/linux/list.h:1006 [inline]
RIP: 0010:namespace_unlock+0x625/0x7a0 fs/namespace.c:1722
Code: df 41 80 3c 07 00 74 08 4c 89 e7 e8 45 26 e3 ff 4c 89 64 24 18 4d 8b 24 24 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 0d 27 e3 ff 49 89 1c 24 48 85 db 74
RSP: 0018:ffffc90006197ca0 EFLAGS: 00010a06
RAX: 1bd5a00000000024 RBX: dead000000000100 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffc90006197b40 RDI: ffffffff8e763678
RBP: ffffc90006197d88 R08: ffffffff90123cf7 R09: 1ffffffff202479e
R10: dffffc0000000000 R11: fffffbfff202479f R12: dead000000000122
R13: ffff88807bedee00 R14: 1ffff1100f7dbddf R15: 1ffff1100f7dbde0
FS: 00007fad7e5a06c0(0000) GS:ffff888125448000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7ab4dad52f CR3: 0000000027f18000 CR4: 00000000003526f0
Call Trace:
<TASK>
__fput+0x766/0x8c0 fs/file_table.c:510
fput_close_sync+0x11f/0x240 fs/file_table.c:605
__do_sys_close fs/open.c:1509 [inline]
__se_sys_close fs/open.c:1494 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1494
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fad7d79c799
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:00007fad7e5a0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007fad7da15fa0 RCX: 00007fad7d79c799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fad7d832c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fad7da16038 R14: 00007fad7da15fa0 R15: 00007ffc68046b08
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__hlist_del include/linux/list.h:992 [inline]
RIP: 0010:hlist_del include/linux/list.h:1006 [inline]
RIP: 0010:namespace_unlock+0x625/0x7a0 fs/namespace.c:1722
Code: df 41 80 3c 07 00 74 08 4c 89 e7 e8 45 26 e3 ff 4c 89 64 24 18 4d 8b 24 24 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 0d 27 e3 ff 49 89 1c 24 48 85 db 74
RSP: 0018:ffffc90006197ca0 EFLAGS: 00010a06
RAX: 1bd5a00000000024 RBX: dead000000000100 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffc90006197b40 RDI: ffffffff8e763678
RBP: ffffc90006197d88 R08: ffffffff90123cf7 R09: 1ffffffff202479e
R10: dffffc0000000000 R11: fffffbfff202479f R12: dead000000000122
R13: ffff88807bedee00 R14: 1ffff1100f7dbddf R15: 1ffff1100f7dbde0
FS: 00007fad7e5a06c0(0000) GS:ffff888125448000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa7e8de7158 CR3: 0000000027f18000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: df 41 80 filds -0x80(%rcx)
3: 3c 07 cmp $0x7,%al
5: 00 74 08 4c add %dh,0x4c(%rax,%rcx,1)
9: 89 e7 mov %esp,%edi
b: e8 45 26 e3 ff call 0xffe32655
10: 4c 89 64 24 18 mov %r12,0x18(%rsp)
15: 4d 8b 24 24 mov (%r12),%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 0d 27 e3 ff call 0xffe32745
38: 49 89 1c 24 mov %rbx,(%r12)
3c: 48 85 db test %rbx,%rbx
3f: 74 .byte 0x74


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