[v6.1] kernel BUG in jfs_unlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=126c32ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=61bee673a2dcf3d442d1
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=150f116a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=132b0b6c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b48d0ca47655/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=17749348580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+61bee6...@syzkaller.appspotmail.com

BUG at fs/jfs/namei.c:513 assert(ip->i_nlink)
------------[ cut here ]------------
kernel BUG at fs/jfs/namei.c:513!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4419 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : jfs_unlink+0x8ec/0x954 fs/jfs/namei.c:513
lr : jfs_unlink+0x8ec/0x954 fs/jfs/namei.c:513
sp : ffff800020b77a80
x29: ffff800020b77b70 x28: dfff800000000000 x27: ffff70000416ef58
x26: dfff800000000000 x25: ffff800020b77ac0 x24: 0000000000000000
x23: 1ffff00002afad68 x22: ffff0000eab82660 x21: ffff0000eab82930
x20: ffff0000eabb3298 x19: ffff0000eabb3270 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d92bc x15: 0000000000000000
x14: 0000000000000001 x13: 1ffff0000416eeb8 x12: 0000000000ff0100
x11: ff00800008311668 x10: 0000000000000000 x9 : 3f48d075f701e500
x8 : 3f48d075f701e500 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800020b77558 x4 : ffff800015304cc0 x3 : ffff80000a891730
x2 : ffff00019f552d10 x1 : 0000000100000000 x0 : 000000000000002d
Call trace:
jfs_unlink+0x8ec/0x954 fs/jfs/namei.c:513
vfs_unlink+0x2e0/0x4f4 fs/namei.c:4330
do_unlinkat+0x328/0x500 fs/namei.c:4398
__do_sys_unlinkat fs/namei.c:4441 [inline]
__se_sys_unlinkat fs/namei.c:4434 [inline]
__arm64_sys_unlinkat+0xe0/0xfc fs/namei.c:4434
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: 90043503 91178063 52804022 959e15d7 (d4210000)
---[ end trace 0000000000000000 ]---


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