Re: [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat

[syzbot <syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in filename_symlinkat

------------[ cut here ]------------
DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff888046fac318, owner = 0x0, curr 0xffff888034380000, list empty
WARNING: kernel/locking/rwsem.c:1381 at __up_write kernel/locking/rwsem.c:1380 [inline], CPU#0: syz.0.17/5821
WARNING: kernel/locking/rwsem.c:1381 at up_write+0x2d6/0x410 kernel/locking/rwsem.c:1643, CPU#0: syz.0.17/5821
Modules linked in:
CPU: 0 UID: 0 PID: 5821 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__up_write kernel/locking/rwsem.c:1380 [inline]
RIP: 0010:up_write+0x388/0x410 kernel/locking/rwsem.c:1643
Code: cc 8b 49 c7 c2 80 eb cc 8b 4c 0f 44 d0 48 8b 7c 24 08 48 c7 c6 e0 ed cc 8b 48 8b 14 24 4c 89 f1 4d 89 e0 4c 8b 4c 24 10 41 52 <67> 48 0f b9 3a 48 83 c4 08 e8 7a a0 0b 03 e9 67 fd ff ff 48 c7 c1
RSP: 0018:ffffc90004e77d80 EFLAGS: 00010246
RAX: ffffffff8bcceb60 RBX: ffff888046fac318 RCX: ffff888046fac318
RDX: 0000000000000000 RSI: ffffffff8bccede0 RDI: ffffffff901506e0
RBP: ffff888046fac370 R08: 0000000000000000 R09: ffff888034380000
R10: ffffffff8bcceb60 R11: ffffed1008df5865 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888046fac318 R15: 1ffff11008df5864
FS:  00007f56261876c0(0000) GS:ffff88808ca58000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000037fcc000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 inode_unlock include/linux/fs.h:1038 [inline]
 end_creating_path fs/namei.c:4963 [inline]
 filename_symlinkat+0x20a/0x430 fs/namei.c:5645
 __do_sys_symlinkat fs/namei.c:5663 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5658
 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: 0033:0x7f562539c799
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:00007f5626187028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f5625616090 RCX: 00007f562539c799
RDX: 00002000000003c0 RSI: 0000000000000007 RDI: 0000200000000240
RBP: 00007f5625432bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5625616128 R14: 00007f5625616090 R15: 00007ffcc1726508
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	49 c7 c2 80 eb cc 8b 	mov    $0xffffffff8bcceb80,%r10
   7:	4c 0f 44 d0          	cmove  %rax,%r10
   b:	48 8b 7c 24 08       	mov    0x8(%rsp),%rdi
  10:	48 c7 c6 e0 ed cc 8b 	mov    $0xffffffff8bccede0,%rsi
  17:	48 8b 14 24          	mov    (%rsp),%rdx
  1b:	4c 89 f1             	mov    %r14,%rcx
  1e:	4d 89 e0             	mov    %r12,%r8
  21:	4c 8b 4c 24 10       	mov    0x10(%rsp),%r9
  26:	41 52                	push   %r10
* 28:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2d:	48 83 c4 08          	add    $0x8,%rsp
  31:	e8 7a a0 0b 03       	call   0x30ba0b0
  36:	e9 67 fd ff ff       	jmp    0xfffffda2
  3b:	48                   	rex.W
  3c:	c7                   	.byte 0xc7
  3d:	c1                   	.byte 0xc1


Tested on:

commit:         5ee8dbf5 Merge tag 'fsverity-for-linus' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=163658d6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c5c49ee0942d1cdb
dashboard link: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=118d1552580000