[v6.6] possible deadlock in mnt_want_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a1153c0deb44 Linux 6.6.147
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=175acdb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=23cd16f26e4e42571f8d
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f646bfa1b52/disk-a1153c0d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a2aec2e8f0fd/vmlinux-a1153c0d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a7abe1f87405/bzImage-a1153c0d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+23cd16...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.3520/19323 is trying to acquire lock:
ffff88806aa42418 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:412

but task is already holding lock:
ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: open_last_lookups fs/namei.c:3561 [inline]
ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: path_openat+0x7f4/0x3270 fs/namei.c:3798

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
inode_lock_shared include/linux/fs.h:814 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1718
walk_component+0x2ad/0x3e0 fs/namei.c:2010
lookup_last fs/namei.c:2467 [inline]
path_lookupat+0x148/0x420 fs/namei.c:2491
filename_lookup+0x22d/0x580 fs/namei.c:2520
kern_path+0x35/0x50 fs/namei.c:2618
lookup_bdev+0xc9/0x290 block/bdev.c:989
resume_store+0x170/0x4c0 kernel/power/hibernate.c:1187
kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x474/0x9a0 fs/read_write.c:584
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (&of->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
kernfs_file_read_iter fs/kernfs/file.c:258 [inline]
kernfs_fop_read_iter+0x18e/0x680 fs/kernfs/file.c:298
__kernel_read+0x2e5/0x730 fs/read_write.c:428
integrity_kernel_read+0x8a/0xd0 security/integrity/iint.c:221
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
ima_calc_file_hash+0xb1f/0x1960 security/integrity/ima/ima_crypto.c:573
ima_collect_measurement+0x4d4/0xa30 security/integrity/ima/ima_api.c:290
process_measurement+0x123a/0x1d50 security/integrity/ima/ima_main.c:370
ima_file_check+0xcc/0x110 security/integrity/ima/ima_main.c:568
do_open fs/namei.c:3642 [inline]
path_openat+0x2910/0x3270 fs/namei.c:3801
do_filp_open+0x1f2/0x430 fs/namei.c:3828
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&iint_mutex_key[depth]){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
process_measurement+0x739/0x1d50 security/integrity/ima/ima_main.c:275
ima_file_check+0xcc/0x110 security/integrity/ima/ima_main.c:568
do_open fs/namei.c:3642 [inline]
path_openat+0x2910/0x3270 fs/namei.c:3801
do_filp_open+0x1f2/0x430 fs/namei.c:3828
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (sb_writers#5){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1633 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1708
mnt_want_write+0x41/0x90 fs/namespace.c:412
ovl_create_object+0xb5/0x2a0 fs/overlayfs/dir.c:626
lookup_open fs/namei.c:3496 [inline]
open_last_lookups fs/namei.c:3564 [inline]
path_openat+0x1705/0x3270 fs/namei.c:3798
do_filp_open+0x1f2/0x430 fs/namei.c:3828
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_open fs/open.c:1445 [inline]
__se_sys_open fs/open.c:1441 [inline]
__x64_sys_open+0x11f/0x140 fs/open.c:1441
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
sb_writers#5 --> &of->mutex --> &ovl_i_mutex_dir_key[depth]

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ovl_i_mutex_dir_key[depth]);
lock(&of->mutex);
lock(&ovl_i_mutex_dir_key[depth]);
rlock(sb_writers#5);

*** DEADLOCK ***

2 locks held by syz.2.3520/19323:
#0: ffff888065a4a418 (sb_writers#20){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:412
#1: ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#1: ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: open_last_lookups fs/namei.c:3561 [inline]
#1: ffff88805e53c170 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: path_openat+0x7f4/0x3270 fs/namei.c:3798

stack backtrace:
CPU: 1 PID: 19323 Comm: syz.2.3520 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1633 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1708
mnt_want_write+0x41/0x90 fs/namespace.c:412
ovl_create_object+0xb5/0x2a0 fs/overlayfs/dir.c:626
lookup_open fs/namei.c:3496 [inline]
open_last_lookups fs/namei.c:3564 [inline]
path_openat+0x1705/0x3270 fs/namei.c:3798
do_filp_open+0x1f2/0x430 fs/namei.c:3828
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_open fs/open.c:1445 [inline]
__se_sys_open fs/open.c:1441 [inline]
__x64_sys_open+0x11f/0x140 fs/open.c:1441
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f18d7f9e019
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:00007f18d8e78028 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f18d8225fa0 RCX: 00007f18d7f9e019
RDX: 0000000000000080 RSI: 0000000000143142 RDI: 0000200000000000
RBP: 00007f18d803500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f18d8226038 R14: 00007f18d8225fa0 R15: 00007fffd4e9af48
</TASK>


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