[syzbot] [overlayfs?] possible deadlock in ovl_copy_up_start (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 940fcc189c51 Add linux-next specific files for 20230921
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12dea70e680000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f140ae6e669ac24
dashboard link: https://syzkaller.appspot.com/bug?extid=e8628856801e9809216f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b8921b235c24/disk-940fcc18.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c80a9f6bcdd4/vmlinux-940fcc18.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed10a4df6950/bzImage-940fcc18.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e86288...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc2-next-20230921-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/15498 is trying to acquire lock:
ffff88808e717968 (&ovl_i_lock_key[depth]#2){+.+.}-{3:3}, at: ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:630 [inline]
ffff88808e717968 (&ovl_i_lock_key[depth]#2){+.+.}-{3:3}, at: ovl_copy_up_start+0x4d/0x290 fs/overlayfs/util.c:692

but task is already holding lock:
ffff88801d8b13e0 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x893/0x1cc0 security/integrity/ima/ima_main.c:266

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&iint->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
process_measurement+0x893/0x1cc0 security/integrity/ima/ima_main.c:266
ima_file_check+0xc2/0x110 security/integrity/ima/ima_main.c:543
do_open fs/namei.c:3622 [inline]
path_openat+0x17a1/0x29c0 fs/namei.c:3777
do_filp_open+0x1de/0x430 fs/namei.c:3804
do_sys_openat2+0x176/0x1e0 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+0x154/0x1e0 fs/open.c:1441
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (sb_writers#4){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1572 [inline]
sb_start_write include/linux/fs.h:1647 [inline]
ovl_start_write+0xfe/0x2d0 fs/overlayfs/util.c:31
ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:830 [inline]
ovl_do_copy_up fs/overlayfs/copy_up.c:945 [inline]
ovl_copy_up_one+0x16a5/0x3250 fs/overlayfs/copy_up.c:1137
ovl_copy_up_flags+0x189/0x200 fs/overlayfs/copy_up.c:1192
ovl_xattr_set+0x387/0x4e0 fs/overlayfs/xattrs.c:56
__vfs_setxattr+0x173/0x1d0 fs/xattr.c:201
__vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:235
__vfs_setxattr_locked+0x17e/0x250 fs/xattr.c:296
vfs_setxattr+0x146/0x350 fs/xattr.c:322
do_setxattr+0x142/0x170 fs/xattr.c:630
setxattr+0x159/0x170 fs/xattr.c:653
path_setxattr+0x1a3/0x1d0 fs/xattr.c:672
__do_sys_setxattr fs/xattr.c:688 [inline]
__se_sys_setxattr fs/xattr.c:684 [inline]
__x64_sys_setxattr+0xc4/0x160 fs/xattr.c:684
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&ovl_i_lock_key[depth]#2){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:630 [inline]
ovl_copy_up_start+0x4d/0x290 fs/overlayfs/util.c:692
ovl_copy_up_one+0x598/0x3250 fs/overlayfs/copy_up.c:1130
ovl_copy_up_flags+0x189/0x200 fs/overlayfs/copy_up.c:1192
ovl_maybe_copy_up+0x124/0x160 fs/overlayfs/copy_up.c:1222
ovl_open+0x16f/0x330 fs/overlayfs/file.c:166
do_dentry_open+0x88b/0x1730 fs/open.c:929
vfs_open fs/open.c:1063 [inline]
dentry_open+0x13f/0x1d0 fs/open.c:1079
ima_calc_file_hash+0x2c4/0x4a0 security/integrity/ima/ima_crypto.c:558
ima_collect_measurement+0x5e2/0x6f0 security/integrity/ima/ima_api.c:289
process_measurement+0xc87/0x1cc0 security/integrity/ima/ima_main.c:345
ima_file_check+0xc2/0x110 security/integrity/ima/ima_main.c:543
do_open fs/namei.c:3622 [inline]
path_openat+0x17a1/0x29c0 fs/namei.c:3777
do_filp_open+0x1de/0x430 fs/namei.c:3804
do_sys_openat2+0x176/0x1e0 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+0x175/0x210 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
&ovl_i_lock_key[depth]#2 --> sb_writers#4 --> &iint->mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&iint->mutex);
lock(sb_writers#4);
lock(&iint->mutex);
lock(&ovl_i_lock_key[depth]#2);

*** DEADLOCK ***

1 lock held by syz-executor.3/15498:
#0: ffff88801d8b13e0 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x893/0x1cc0 security/integrity/ima/ima_main.c:266

stack backtrace:
CPU: 0 PID: 15498 Comm: syz-executor.3 Not tainted 6.6.0-rc2-next-20230921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
check_noncircular+0x311/0x3f0 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:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:630 [inline]
ovl_copy_up_start+0x4d/0x290 fs/overlayfs/util.c:692
ovl_copy_up_one+0x598/0x3250 fs/overlayfs/copy_up.c:1130
ovl_copy_up_flags+0x189/0x200 fs/overlayfs/copy_up.c:1192
ovl_maybe_copy_up+0x124/0x160 fs/overlayfs/copy_up.c:1222
ovl_open+0x16f/0x330 fs/overlayfs/file.c:166
do_dentry_open+0x88b/0x1730 fs/open.c:929
vfs_open fs/open.c:1063 [inline]
dentry_open+0x13f/0x1d0 fs/open.c:1079
ima_calc_file_hash+0x2c4/0x4a0 security/integrity/ima/ima_crypto.c:558
ima_collect_measurement+0x5e2/0x6f0 security/integrity/ima/ima_api.c:289
process_measurement+0xc87/0x1cc0 security/integrity/ima/ima_main.c:345
ima_file_check+0xc2/0x110 security/integrity/ima/ima_main.c:543
do_open fs/namei.c:3622 [inline]
path_openat+0x17a1/0x29c0 fs/namei.c:3777
do_filp_open+0x1de/0x430 fs/namei.c:3804
do_sys_openat2+0x176/0x1e0 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+0x175/0x210 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f30bf67cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f30c03990c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f30bf79c050 RCX: 00007f30bf67cae9
RDX: 0000000000008443 RSI: 0000000020004280 RDI: ffffffffffffff9c
RBP: 00007f30bf6c847a R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000000cc R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f30bf79c050 R15: 00007ffce77ebe68
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Amir Goldstein]

This looks like a new report that started after:
346f114cc506 ovl: reorder ovl_want_write() after ovl_inode_lock()

but the root cause looks like the same old false positive

#syz dup: possible deadlock in mnt_want_write (2)