[syzbot] [isofs?] VFS: Busy inodes after unmount (use-after-free) (3)

[syzbot <syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    30d4efb2f5a5 Merge tag 'for-linus-6.18-rc1-tag' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1350d05b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5eb55ce880562a8c
dashboard link: https://syzkaller.appspot.com/bug?extid=1d79ebe5383fc016cf07
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14f17c14580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13d80a7c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b7f58792107b/disk-30d4efb2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9a0647491b90/vmlinux-30d4efb2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9829a72408d5/bzImage-30d4efb2.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/ec44ab2c5fdc/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com

VFS: Busy inodes after unmount of loop0 (iso9660)
------------[ cut here ]------------
kernel BUG at fs/super.c:653!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 5985 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:generic_shutdown_super+0x2bc/0x2c0 fs/super.c:651
Code: 03 42 80 3c 28 00 74 08 4c 89 f7 e8 6e 32 f3 ff 49 8b 16 48 81 c3 d0 07 00 00 48 c7 c7 60 90 d8 8a 48 89 de e8 85 59 fe fe 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f
RSP: 0018:ffffc9000419fd20 EFLAGS: 00010246
RAX: 0000000000000031 RBX: ffff88803956a7d0 RCX: 8b706059fb7f3300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 1ffff110072ad51b R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff52000833f49 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffffff8d5b82e0 R15: ffff88803956a8d8
FS:  0000555590698500(0000) GS:ffff888127125000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055bb0ed4b1b8 CR3: 0000000028c78000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 kill_block_super+0x44/0x90 fs/super.c:1723
 deactivate_locked_super+0xb9/0x130 fs/super.c:474
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1318
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff17a1f01f7
Code: a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fff2497d5b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007ff17a271d7d RCX: 00007ff17a1f01f7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff2497d670
RBP: 00007fff2497d670 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007fff2497e700
R13: 00007ff17a271d7d R14: 000000000001bfd3 R15: 00007fff2497e740
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:generic_shutdown_super+0x2bc/0x2c0 fs/super.c:651
Code: 03 42 80 3c 28 00 74 08 4c 89 f7 e8 6e 32 f3 ff 49 8b 16 48 81 c3 d0 07 00 00 48 c7 c7 60 90 d8 8a 48 89 de e8 85 59 fe fe 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f
RSP: 0018:ffffc9000419fd20 EFLAGS: 00010246
RAX: 0000000000000031 RBX: ffff88803956a7d0 RCX: 8b706059fb7f3300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 1ffff110072ad51b R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff52000833f49 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffffff8d5b82e0 R15: ffff88803956a8d8
FS:  0000555590698500(0000) GS:ffff888127125000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055bb0ed4b1b8 CR3: 0000000028c78000 CR4: 00000000003526f0


---
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