Re: [syzbot] possible deadlock in __jbd2_log_wait_for_space

From: syzbot
Date: Fri Nov 18 2022 - 23:50:49 EST

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syzbot has found a reproducer for the following issue on:

HEAD commit: 15f3bff12cf6 Add linux-next specific files for 20221116
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1370fb65880000
kernel config: https://syzkaller.appspot.com/x/.config?x=ec2a1d4f50866178
dashboard link: https://syzkaller.appspot.com/bug?extid=fa1bbda326271b8808c9
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=114241dd880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14c2f42d880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b67307c8c3c9/disk-15f3bff1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/956c7b56c5c1/vmlinux-15f3bff1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/505ae2f65529/bzImage-15f3bff1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fa1bbda326271b8808c9@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc5-next-20221116-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor164/5304 is trying to acquire lock:
ffff88814baea3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: __jbd2_log_wait_for_space+0x238/0x460 fs/jbd2/checkpoint.c:110

but task is already holding lock:
ffff888065608e08 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
ffff888065608e08 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: vfs_unlink+0xd9/0x930 fs/namei.c:4240

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#8){++++}-{3:3}:
down_read+0x9c/0x450 kernel/locking/rwsem.c:1509
inode_lock_shared include/linux/fs.h:766 [inline]
ext4_bmap+0x52/0x470 fs/ext4/inode.c:3164
bmap+0xae/0x120 fs/inode.c:1798
jbd2_journal_bmap+0xac/0x180 fs/jbd2/journal.c:977
__jbd2_journal_erase fs/jbd2/journal.c:1789 [inline]
jbd2_journal_flush+0x853/0xc00 fs/jbd2/journal.c:2492
ext4_ioctl_checkpoint fs/ext4/ioctl.c:1081 [inline]
__ext4_ioctl+0xae8/0x4d60 fs/ext4/ioctl.c:1586
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
mutex_lock_io_nested+0x143/0x11a0 kernel/locking/mutex.c:833
__jbd2_log_wait_for_space+0x238/0x460 fs/jbd2/checkpoint.c:110
add_transaction_credits+0xa2d/0xb70 fs/jbd2/transaction.c:298
start_this_handle+0x3ae/0x14a0 fs/jbd2/transaction.c:422
jbd2__journal_start+0x39d/0x9b0 fs/jbd2/transaction.c:520
__ext4_journal_start_sb+0x421/0x530 fs/ext4/ext4_jbd2.c:105
__ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline]
ext4_unlink+0x32b/0xae0 fs/ext4/namei.c:3284
vfs_unlink+0x355/0x930 fs/namei.c:4251
do_unlinkat+0x3b7/0x640 fs/namei.c:4319
__do_sys_unlink fs/namei.c:4367 [inline]
__se_sys_unlink fs/namei.c:4365 [inline]
__x64_sys_unlink+0xca/0x110 fs/namei.c:4365
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#8);
lock(&journal->j_checkpoint_mutex);
lock(&sb->s_type->i_mutex_key#8);
lock(&journal->j_checkpoint_mutex);

*** DEADLOCK ***

3 locks held by syz-executor164/5304:
#0: ffff88814bae6460 (sb_writers#4){.+.+}-{0:0}, at: do_unlinkat+0x183/0x640 fs/namei.c:4298
#1: ffff888076c1d440 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:791 [inline]
#1: ffff888076c1d440 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: do_unlinkat+0x270/0x640 fs/namei.c:4302
#2: ffff888065608e08 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
#2: ffff888065608e08 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: vfs_unlink+0xd9/0x930 fs/namei.c:4240

stack backtrace:
CPU: 1 PID: 5304 Comm: syz-executor164 Not tainted 6.1.0-rc5-next-20221116-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
mutex_lock_io_nested+0x143/0x11a0 kernel/locking/mutex.c:833
__jbd2_log_wait_for_space+0x238/0x460 fs/jbd2/checkpoint.c:110
add_transaction_credits+0xa2d/0xb70 fs/jbd2/transaction.c:298
start_this_handle+0x3ae/0x14a0 fs/jbd2/transaction.c:422
jbd2__journal_start+0x39d/0x9b0 fs/jbd2/transaction.c:520
__ext4_journal_start_sb+0x421/0x530 fs/ext4/ext4_jbd2.c:105
__ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline]
ext4_unlink+0x32b/0xae0 fs/ext4/namei.c:3284
vfs_unlink+0x355/0x930 fs/namei.c:4251
do_unlinkat+0x3b7/0x640 fs/namei.c:4319
__do_sys_unlink fs/namei.c:4367 [inline]
__se_sys_unlink fs/namei.c:4365 [inline]
__x64_sys_unlink+0xca/0x110 fs/namei.c:4365
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3a0088bff7
Code: 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 57 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe6d2c0f28 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3a0088bff7
RDX: 00007ffe6d2c0f50 RSI: 00007ffe6d2c0f50 RDI: 00007ffe6d2c0fe0
RBP: 00007ffe6d2c0fe0 R08: 0000000000000001 R09: 00007ffe6d2c0dc0
R10: 0000555555f9e683 R11: 0000000000000206 R12: 00007ffe6d2c20a0
R13: 0000555555f9e5f0 R14: 00007ffe6d2c0f50 R15: 431bde82d7b634db
</TASK>

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