possible deadlock in btrfs_start_transaction

Status: auto-obsoleted due to no activity on 2024/12/10 18:05
Reported-by: syzbot+042fae30e157a8ed4728@syzkaller.appspotmail.com
First crash: 729d, last: 690d
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in btrfs_start_transaction (2) origin:upstream 4 C error 8 6d18h 537d 0/3 upstream: reported C repro on 2025/02/02 07:03

Sample crash report:
BTRFS info (device loop4): has skinny extents
BTRFS info (device loop4): enabling ssd optimizations
======================================================
WARNING: possible circular locking dependency detected
5.15.165-syzkaller #0 Not tainted
------------------------------------------------------
syz.4.159/4799 is trying to acquire lock:
ffff0000ebee6650 (sb_internal#3){.+.+}-{0:0}, at: btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:777

but task is already holding lock:
ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: open_last_lookups fs/namei.c:3529 [inline]
ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: path_openat+0x640/0x26cc fs/namei.c:3739

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&type->i_mutex_dir_key#10){++++}-{3:3}:
       down_read+0xc0/0x398 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:799 [inline]
       lookup_slow+0x50/0x84 fs/namei.c:1679
       walk_component+0x394/0x4cc fs/namei.c:1976
       lookup_last fs/namei.c:2431 [inline]
       path_lookupat+0x13c/0x3d0 fs/namei.c:2455
       filename_lookup+0x1c4/0x4c8 fs/namei.c:2484
       kern_path+0x4c/0x194 fs/namei.c:2582
       lookup_bdev+0xc0/0x25c block/bdev.c:979
       device_matched fs/btrfs/volumes.c:568 [inline]
       btrfs_free_stale_devices+0x658/0x9ec fs/btrfs/volumes.c:608
       btrfs_forget_devices+0x5c/0x98 fs/btrfs/volumes.c:1395
       btrfs_control_ioctl+0x12c/0x248 fs/btrfs/super.c:2451
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #2 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
       write_all_supers+0x134c/0x3a6c fs/btrfs/disk-io.c:4159
       btrfs_sync_log+0x19c8/0x2294 fs/btrfs/tree-log.c:3327
       btrfs_sync_file+0xa0c/0xf54 fs/btrfs/file.c:2378
       vfs_fsync_range+0x168/0x188 fs/sync.c:188
       generic_write_sync include/linux/fs.h:2984 [inline]
       btrfs_file_write_iter+0x5a8/0xc80 fs/btrfs/file.c:2111
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x884/0xb44 fs/read_write.c:594
       ksys_write+0x15c/0x26c fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
       btrfs_sync_log+0x1904/0x2294 fs/btrfs/tree-log.c:3308
       btrfs_sync_file+0xa0c/0xf54 fs/btrfs/file.c:2378
       vfs_fsync_range+0x168/0x188 fs/sync.c:188
       generic_write_sync include/linux/fs.h:2984 [inline]
       btrfs_file_write_iter+0x5a8/0xc80 fs/btrfs/file.c:2111
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x884/0xb44 fs/read_write.c:594
       ksys_write+0x15c/0x26c fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (sb_internal#3){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
       lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_intwrite include/linux/fs.h:1928 [inline]
       start_transaction+0x644/0x1480 fs/btrfs/transaction.c:678
       btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:777
       btrfs_create+0x134/0x56c fs/btrfs/inode.c:6892
       lookup_open fs/namei.c:3462 [inline]
       open_last_lookups fs/namei.c:3532 [inline]
       path_openat+0xf18/0x26cc fs/namei.c:3739
       do_filp_open+0x1a8/0x3b4 fs/namei.c:3769
       do_sys_openat2+0x128/0x3e0 fs/open.c:1253
       do_sys_open fs/open.c:1269 [inline]
       __do_sys_openat fs/open.c:1285 [inline]
       __se_sys_openat fs/open.c:1280 [inline]
       __arm64_sys_openat+0x1f0/0x240 fs/open.c:1280
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  sb_internal#3 --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#10

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->i_mutex_dir_key#10);
                               lock(&fs_devs->device_list_mutex);
                               lock(&type->i_mutex_dir_key#10);
  lock(sb_internal#3);

 *** DEADLOCK ***

2 locks held by syz.4.159/4799:
 #0: ffff0000ebee6460 (sb_writers#14){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:377
 #1: ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
 #1: ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: open_last_lookups fs/namei.c:3529 [inline]
 #1: ffff0000e0255e60 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: path_openat+0x640/0x26cc fs/namei.c:3739

stack backtrace:
CPU: 1 PID: 4799 Comm: syz.4.159 Not tainted 5.15.165-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2011
 check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
 lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1811 [inline]
 sb_start_intwrite include/linux/fs.h:1928 [inline]
 start_transaction+0x644/0x1480 fs/btrfs/transaction.c:678
 btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:777
 btrfs_create+0x134/0x56c fs/btrfs/inode.c:6892
 lookup_open fs/namei.c:3462 [inline]
 open_last_lookups fs/namei.c:3532 [inline]
 path_openat+0xf18/0x26cc fs/namei.c:3739
 do_filp_open+0x1a8/0x3b4 fs/namei.c:3769
 do_sys_openat2+0x128/0x3e0 fs/open.c:1253
 do_sys_open fs/open.c:1269 [inline]
 __do_sys_openat fs/open.c:1285 [inline]
 __se_sys_openat fs/open.c:1280 [inline]
 __arm64_sys_openat+0x1f0/0x240 fs/open.c:1280
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/09/01 18:04 linux-5.15.y fa93fa65db6e 1eda0d14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in btrfs_start_transaction
2024/07/24 14:31 linux-5.15.y 7c6d66f0266f 57b2edb1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in btrfs_start_transaction
* Struck through repros no longer work on HEAD.