Hello.
Commit 87579e9b7d8dc36e ("loop: use worker per cgroup instead of kworker")
is calling destroy_workqueue() with lo->lo_mutex held, and syzbot is
reporting circular locking dependency
&disk->open_mutex => &lo->lo_mutex => (wq_completion)loop$M =>
(work_completion)(&lo->rootcg_work) => sb_writers#$N => &p->lock =>
&of->mutex => system_transition_mutex/1 => &disk->open_mutex
. Can you somehow call destroy_workqueue() without holding a lock (e.g.
breaking &lo->lo_mutex => (wq_completion)loop$M dependency chain by
making sure that below change is safe) ?
@@ -1365,7 +1365,9 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
/* freeze request queue during the transition */
blk_mq_freeze_queue(lo->lo_queue);
+ mutex_unlock(&lo->lo_mutex);
destroy_workqueue(lo->workqueue);
+ mutex_lock(&lo->lo_mutex);
spin_lock_irq(&lo->lo_work_lock);
list_for_each_entry_safe(worker, pos, &lo->idle_worker_list,
idle_list) {
On 2021/09/23 9:52, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 93ff9f13be91 Merge tag 's390-5.15-3' of git://git.kernel.o..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15d5b33d300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=6d93fe4341f98704
> dashboard link: https://syzkaller.appspot.com/bug?extid=384fb45e189bf86b6bb9
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+384fb45e189bf86b6bb9@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.15.0-rc1-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor.3/12106 is trying to acquire lock:
> ffffffff8c201508 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x25/0x1d0 block/genhd.c:634
>
> but task is already holding lock:
> ffffffff8b84fda8 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:932
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #9 (system_transition_mutex/1){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:932
> software_resume kernel/power/hibernate.c:86 [inline]
> resume_store+0x161/0x190 kernel/power/hibernate.c:1179
> kobj_attr_store+0x50/0x80 lib/kobject.c:856
> sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
> kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
> call_write_iter include/linux/fs.h:2163 [inline]
> do_iter_readv_writev+0x472/0x750 fs/read_write.c:729
> do_iter_write+0x188/0x710 fs/read_write.c:855
> vfs_iter_write+0x70/0xa0 fs/read_write.c:896
> iter_file_splice_write+0x723/0xc70 fs/splice.c:689
> do_splice_from fs/splice.c:767 [inline]
> direct_splice_actor+0x110/0x180 fs/splice.c:936
> splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
> do_splice_direct+0x1b3/0x280 fs/splice.c:979
> do_sendfile+0xae9/0x1240 fs/read_write.c:1249
> __do_sys_sendfile64 fs/read_write.c:1314 [inline]
> __se_sys_sendfile64 fs/read_write.c:1300 [inline]
> __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #8 (&of->mutex){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> kernfs_seq_start+0x4b/0x260 fs/kernfs/file.c:112
> seq_read_iter+0x2c7/0x1240 fs/seq_file.c:225
> kernfs_fop_read_iter+0x44f/0x5f0 fs/kernfs/file.c:241
> call_read_iter include/linux/fs.h:2157 [inline]
> new_sync_read+0x421/0x6e0 fs/read_write.c:404
> vfs_read+0x35c/0x600 fs/read_write.c:485
> ksys_read+0x12d/0x250 fs/read_write.c:623
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #7 (&p->lock){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> seq_read_iter+0xdf/0x1240 fs/seq_file.c:182
> call_read_iter include/linux/fs.h:2157 [inline]
> generic_file_splice_read+0x453/0x6d0 fs/splice.c:311
> do_splice_to+0x1bf/0x250 fs/splice.c:796
> splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870
> do_splice_direct+0x1b3/0x280 fs/splice.c:979
> do_sendfile+0xae9/0x1240 fs/read_write.c:1249
> __do_sys_sendfile64 fs/read_write.c:1314 [inline]
> __se_sys_sendfile64 fs/read_write.c:1300 [inline]
> __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #6 (sb_writers#3){.+.+}-{0:0}:
> percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
> __sb_start_write include/linux/fs.h:1812 [inline]
> sb_start_write include/linux/fs.h:1882 [inline]
> file_start_write include/linux/fs.h:3008 [inline]
> lo_write_bvec+0x3b6/0x6d0 drivers/block/loop.c:327
> lo_write_simple drivers/block/loop.c:350 [inline]
> do_req_filebacked drivers/block/loop.c:668 [inline]
> loop_handle_cmd drivers/block/loop.c:2201 [inline]
> loop_process_work+0xc60/0x24e0 drivers/block/loop.c:2241
> process_one_work+0x9bf/0x16b0 kernel/workqueue.c:2297
> worker_thread+0x658/0x11f0 kernel/workqueue.c:2444
> kthread+0x3e5/0x4d0 kernel/kthread.c:319
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>
> -> #5 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
> process_one_work+0x92e/0x16b0 kernel/workqueue.c:2273
> worker_thread+0x658/0x11f0 kernel/workqueue.c:2444
> kthread+0x3e5/0x4d0 kernel/kthread.c:319
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>
> -> #4 ((wq_completion)loop3){+.+.}-{0:0}:
> flush_workqueue+0x110/0x15b0 kernel/workqueue.c:2817
> drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2982
> destroy_workqueue+0x71/0x800 kernel/workqueue.c:4419
> __loop_clr_fd+0x212/0x15e0 drivers/block/loop.c:1368
> lo_release+0x1ac/0x1f0 drivers/block/loop.c:2068
> blkdev_put_whole block/bdev.c:691 [inline]
> blkdev_put+0x2fb/0x9e0 block/bdev.c:953
> blkdev_close+0x8d/0xb0 block/fops.c:459
> __fput+0x288/0x9f0 fs/file_table.c:280
> task_work_run+0xdd/0x1a0 kernel/task_work.c:164
> tracehook_notify_resume include/linux/tracehook.h:189 [inline]
> exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
> exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209
> __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
> syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
> do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #3 (&lo->lo_mutex){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> lo_open+0x75/0x120 drivers/block/loop.c:2040
> blkdev_get_whole+0x99/0x2a0 block/bdev.c:668
> blkdev_get_by_dev.part.0+0x354/0xb60 block/bdev.c:823
> blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
> blkdev_open+0x154/0x2b0 block/fops.c:447
> do_dentry_open+0x4c8/0x11d0 fs/open.c:822
> do_open fs/namei.c:3428 [inline]
> path_openat+0x1c9a/0x2740 fs/namei.c:3561
> do_filp_open+0x1aa/0x400 fs/namei.c:3588
> do_sys_openat2+0x16d/0x4d0 fs/open.c:1200
> do_sys_open fs/open.c:1216 [inline]
> __do_sys_open fs/open.c:1224 [inline]
> __se_sys_open fs/open.c:1220 [inline]
> __x64_sys_open+0x119/0x1c0 fs/open.c:1220
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #2 (&disk->open_mutex){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> bd_register_pending_holders+0x2c/0x470 block/holder.c:160
> device_add_disk+0x74c/0xfc0 block/genhd.c:475
> add_disk include/linux/genhd.h:221 [inline]
> brd_alloc+0x466/0x660 drivers/block/brd.c:413
> brd_init+0x16f/0x276 drivers/block/brd.c:496
> do_one_initcall+0x103/0x650 init/main.c:1303
> do_initcall_level init/main.c:1376 [inline]
> do_initcalls init/main.c:1392 [inline]
> do_basic_setup init/main.c:1411 [inline]
> kernel_init_freeable+0x6b1/0x73a init/main.c:1614
> kernel_init+0x1a/0x1d0 init/main.c:1505
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>
> -> #1 (brd_devices_mutex){+.+.}-{3:3}:
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> brd_probe+0x31/0xe0 drivers/block/brd.c:428
> blk_request_module+0x111/0x1d0 block/genhd.c:637
> blkdev_get_no_open+0x178/0x1e0 block/bdev.c:739
> blkdev_get_by_dev.part.0+0x22/0xb60 block/bdev.c:803
> blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
> blkdev_open+0x154/0x2b0 block/fops.c:447
> do_dentry_open+0x4c8/0x11d0 fs/open.c:822
> do_open fs/namei.c:3428 [inline]
> path_openat+0x1c9a/0x2740 fs/namei.c:3561
> do_filp_open+0x1aa/0x400 fs/namei.c:3588
> do_sys_openat2+0x16d/0x4d0 fs/open.c:1200
> do_sys_open fs/open.c:1216 [inline]
> __do_sys_openat fs/open.c:1232 [inline]
> __se_sys_openat fs/open.c:1227 [inline]
> __x64_sys_openat+0x13f/0x1f0 fs/open.c:1227
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #0 (major_names_lock){+.+.}-{3:3}:
> check_prev_add kernel/locking/lockdep.c:3051 [inline]
> check_prevs_add kernel/locking/lockdep.c:3174 [inline]
> validate_chain kernel/locking/lockdep.c:3789 [inline]
> __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
> lock_acquire kernel/locking/lockdep.c:5625 [inline]
> lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> blk_request_module+0x25/0x1d0 block/genhd.c:634
> blkdev_get_no_open+0x178/0x1e0 block/bdev.c:739
> blkdev_get_by_dev.part.0+0x22/0xb60 block/bdev.c:803
> blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
> swsusp_check+0x4d/0x270 kernel/power/swap.c:1525
> software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:977
> software_resume kernel/power/hibernate.c:86 [inline]
> resume_store+0x161/0x190 kernel/power/hibernate.c:1179
> kobj_attr_store+0x50/0x80 lib/kobject.c:856
> sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
> kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
> call_write_iter include/linux/fs.h:2163 [inline]
> do_iter_readv_writev+0x472/0x750 fs/read_write.c:729
> do_iter_write+0x188/0x710 fs/read_write.c:855
> vfs_iter_write+0x70/0xa0 fs/read_write.c:896
> iter_file_splice_write+0x723/0xc70 fs/splice.c:689
> do_splice_from fs/splice.c:767 [inline]
> direct_splice_actor+0x110/0x180 fs/splice.c:936
> splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
> do_splice_direct+0x1b3/0x280 fs/splice.c:979
> do_sendfile+0xae9/0x1240 fs/read_write.c:1249
> __do_sys_sendfile64 fs/read_write.c:1314 [inline]
> __se_sys_sendfile64 fs/read_write.c:1300 [inline]
> __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> other info that might help us debug this:
>
> Chain exists of:
> major_names_lock --> &of->mutex --> system_transition_mutex/1
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(system_transition_mutex/1);
> lock(&of->mutex);
> lock(system_transition_mutex/1);
> lock(major_names_lock);
>
> *** DEADLOCK ***
>
> 4 locks held by syz-executor.3/12106:
> #0: ffff88807ec32460 (sb_writers#6){.+.+}-{0:0}, at: __do_sys_sendfile64 fs/read_write.c:1314 [inline]
> #0: ffff88807ec32460 (sb_writers#6){.+.+}-{0:0}, at: __se_sys_sendfile64 fs/read_write.c:1300 [inline]
> #0: ffff88807ec32460 (sb_writers#6){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
> #1: ffff888075c42088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x287/0x500 fs/kernfs/file.c:287
> #2: ffff888015db0830 (kn->active#594){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ab/0x500 fs/kernfs/file.c:288
> #3: ffffffff8b84fda8 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:932
>
> stack backtrace:
> CPU: 1 PID: 12106 Comm: syz-executor.3 Not tainted 5.15.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131
> check_prev_add kernel/locking/lockdep.c:3051 [inline]
> check_prevs_add kernel/locking/lockdep.c:3174 [inline]
> validate_chain kernel/locking/lockdep.c:3789 [inline]
> __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
> lock_acquire kernel/locking/lockdep.c:5625 [inline]
> lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
> __mutex_lock_common kernel/locking/mutex.c:596 [inline]
> __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
> blk_request_module+0x25/0x1d0 block/genhd.c:634
> blkdev_get_no_open+0x178/0x1e0 block/bdev.c:739
> blkdev_get_by_dev.part.0+0x22/0xb60 block/bdev.c:803
> blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
> swsusp_check+0x4d/0x270 kernel/power/swap.c:1525
> software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:977
> software_resume kernel/power/hibernate.c:86 [inline]
> resume_store+0x161/0x190 kernel/power/hibernate.c:1179
> kobj_attr_store+0x50/0x80 lib/kobject.c:856
> sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
> kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
> call_write_iter include/linux/fs.h:2163 [inline]
> do_iter_readv_writev+0x472/0x750 fs/read_write.c:729
> do_iter_write+0x188/0x710 fs/read_write.c:855
> vfs_iter_write+0x70/0xa0 fs/read_write.c:896
> iter_file_splice_write+0x723/0xc70 fs/splice.c:689
> do_splice_from fs/splice.c:767 [inline]
> direct_splice_actor+0x110/0x180 fs/splice.c:936
> splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
> do_splice_direct+0x1b3/0x280 fs/splice.c:979
> do_sendfile+0xae9/0x1240 fs/read_write.c:1249
> __do_sys_sendfile64 fs/read_write.c:1314 [inline]
> __se_sys_sendfile64 fs/read_write.c:1300 [inline]
> __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f74925ad739
> 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 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f748fb24188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 00007f74926b1f80 RCX: 00007f74925ad739
> RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
> RBP: 00007f7492607cc4 R08: 0000000000000000 R09: 0000000000000000
> R10: 000000000000000c R11: 0000000000000246 R12: 00007f74926b1f80
> R13: 00007fff0a996b3f R14: 00007f748fb24300 R15: 0000000000022000
> PM: Image not found (code -6)
>
>
> ---
> 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 syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
