Message-ID: <6727d567.050a0220.3c8d68.0a91.GAE@google.com>
Date: Sun, 03 Nov 2024 11:56:23 -0800
From: syzbot <syzbot+625941ecc67c107ef2bd@...kaller.appspotmail.com>
To: linkinjeon@...nel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, sj1557.seo@...sung.com, 
	syzkaller-bugs@...glegroups.com, yuezhang.mo@...y.com
Subject: [syzbot] [exfat?] possible deadlock in __generic_file_fsync (2)

Hello,

syzbot found the following issue on:

HEAD commit:    86e3904dcdc7 Add linux-next specific files for 20241030
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1578a55f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=328572ed4d152be9
dashboard link: https://syzkaller.appspot.com/bug?extid=625941ecc67c107ef2bd
compiler:       Debian clang version 15.0.6, 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/f584828ac0fd/disk-86e3904d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/09481d17f87a/vmlinux-86e3904d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ebed9a1794c3/bzImage-86e3904d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+625941ecc67c107ef2bd@...kaller.appspotmail.com

exfat: Deprecated parameter 'namecase'
exfat: Deprecated parameter 'utf8'
exFAT-fs (loop1): failed to load upcase table (idx : 0x00012153, chksum : 0x822ffc2e, utbl_chksum : 0xe619d30d)
======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc5-next-20241030-syzkaller #0 Not tainted
------------------------------------------------------
syz.1.67/6116 is trying to acquire lock:
ffff888063a215f0 (&sb->s_type->i_mutex_key#21){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:816 [inline]
ffff888063a215f0 (&sb->s_type->i_mutex_key#21){+.+.}-{4:4}, at: __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536

but task is already holding lock:
ffff8880253d1db8 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_freeze_queue block/blk-mq.c:177 [inline]
ffff8880253d1db8 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_mq_freeze_queue+0x15/0x20 block/blk-mq.c:187

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&q->q_usage_counter(io)
#17){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       bio_queue_enter block/blk.h:75 [inline]
       blk_mq_submit_bio+0x1510/0x2490 block/blk-mq.c:3069
       __submit_bio+0x2c2/0x560 block/blk-core.c:629
       __submit_bio_noacct_mq block/blk-core.c:710 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:739
       submit_bh fs/buffer.c:2819 [inline]
       __sync_dirty_buffer+0x23d/0x390 fs/buffer.c:2857
       exfat_set_volume_dirty+0x5d/0x80 fs/exfat/super.c:124
       exfat_create+0x1aa/0x5a0 fs/exfat/namei.c:554
       lookup_open fs/namei.c:3595 [inline]
       open_last_lookups fs/namei.c:3694 [inline]
       path_openat+0x1c03/0x3590 fs/namei.c:3930
       do_filp_open+0x235/0x490 fs/namei.c:3960
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1419
       do_sys_open fs/open.c:1434 [inline]
       __do_sys_open fs/open.c:1442 [inline]
       __se_sys_open fs/open.c:1438 [inline]
       __x64_sys_open+0x225/0x270 fs/open.c:1438
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&sbi->s_lock){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       exfat_lookup+0x140/0x18f0 fs/exfat/namei.c:701
       lookup_open fs/namei.c:3573 [inline]
       open_last_lookups fs/namei.c:3694 [inline]
       path_openat+0x11a7/0x3590 fs/namei.c:3930
       do_filp_open+0x235/0x490 fs/namei.c:3960
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1419
       do_sys_open fs/open.c:1434 [inline]
       __do_sys_open fs/open.c:1442 [inline]
       __se_sys_open fs/open.c:1438 [inline]
       __x64_sys_open+0x225/0x270 fs/open.c:1438
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sb->s_type->i_mutex_key#21){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_write+0x99/0x220 kernel/locking/rwsem.c:1577
       inode_lock include/linux/fs.h:816 [inline]
       __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536
       exfat_file_fsync+0xf9/0x1d0 fs/exfat/file.c:524
       __loop_update_dio+0x1a4/0x500 drivers/block/loop.c:204
       loop_set_status+0x62b/0x8f0 drivers/block/loop.c:1290
       lo_ioctl+0xcbc/0x1f50
       blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &sb->s_type->i_mutex_key#21 --> &sbi->s_lock --> &q->q_usage_counter(io)#17

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&q->q_usage_counter(io)#17);
                               lock(&sbi->s_lock);
                               lock(&q->q_usage_counter(io)#17);
  lock(&sb->s_type->i_mutex_key#21);

 *** DEADLOCK ***

3 locks held by syz.1.67/6116:
 #0: ffff888020f07360 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0x8f0 drivers/block/loop.c:1252
 #1: ffff8880253d1db8 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_freeze_queue block/blk-mq.c:177 [inline]
 #1: ffff8880253d1db8 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_mq_freeze_queue+0x15/0x20 block/blk-mq.c:187
 #2: ffff8880253d1df0 (&q->q_usage_counter(queue)){+.+.}-{0:0}, at: blk_freeze_queue block/blk-mq.c:177 [inline]
 #2: ffff8880253d1df0 (&q->q_usage_counter(queue)){+.+.}-{0:0}, at: blk_mq_freeze_queue+0x15/0x20 block/blk-mq.c:187

stack backtrace:
CPU: 0 UID: 0 PID: 6116 Comm: syz.1.67 Not tainted 6.12.0-rc5-next-20241030-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 down_write+0x99/0x220 kernel/locking/rwsem.c:1577
 inode_lock include/linux/fs.h:816 [inline]
 __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536
 exfat_file_fsync+0xf9/0x1d0 fs/exfat/file.c:524
 __loop_update_dio+0x1a4/0x500 drivers/block/loop.c:204
 loop_set_status+0x62b/0x8f0 drivers/block/loop.c:1290
 lo_ioctl+0xcbc/0x1f50
 blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9dbcd7e719
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9dbdb6a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9dbcf35f80 RCX: 00007f9dbcd7e719
RDX: 0000000020001300 RSI: 0000000000004c04 RDI: 0000000000000005
RBP: 00007f9dbcdf132e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9dbcf35f80 R15: 00007ffee1d5a118
 </TASK>


---
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