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* Potential Linux Crash:  possible deadlock in do_lock_mount   in linux6.12.24(longterm maintenance)
@ 2025-04-27  2:28 Jianzhou Zhao
  2025-04-28 11:46 ` Jan Kara
  0 siblings, 1 reply; 2+ messages in thread
From: Jianzhou Zhao @ 2025-04-27  2:28 UTC (permalink / raw)
  To: stable; +Cc: viro, brauner, jack, linux-fsdevel, linux-kernel

Hello, I found a potential bug titled "  possible deadlock in do_lock_mount " with modified syzkaller in the  Linux6.12.24(longterm maintenance, last updated on April 20, 2025).
(The latest version of 6.12 is 6.12-25 at present. However, after comparison, I found that there seems to be no fix for this bug in the latest version.)
Unfortunately, I am unable to reproduce this bug.
If you fix this issue, please add the following tag to the commit:  Reported-by: Jianzhou Zhao <luckd0g@163.com>,    xingwei lee <xrivendell7@gmail.com>
The commit of the kernel is : b6efa8ce222e58cfe2bbaa4e3329818c2b4bd74e
kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=55f8591b98dd132
compiler: gcc version 11.4.0

------------[ cut here ]-----------------------------------------
 TITLE:  possible deadlock in do_lock_mount
------------[ cut here ]------------
======================================================
======================================================
WARNING: possible circular locking dependency detected
6.12.24 #3 Not tainted
------------------------------------------------------
syz.6.1765/29153 is trying to acquire lock:
ffffffff8e14afc0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline]
ffffffff8e14afc0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4058 [inline]
ffffffff8e14afc0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4136 [inline]
ffffffff8e14afc0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x4b/0x310 mm/slub.c:4312

but task is already holding lock:
ffffffff8e1bfdd0 (namespace_sem){++++}-{3:3}, at: namespace_lock fs/namespace.c:1713 [inline]
ffffffff8e1bfdd0 (namespace_sem){++++}-{3:3}, at: do_lock_mount+0x150/0x5b0 fs/namespace.c:2618

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (namespace_sem){++++}-{3:3}:
       down_write+0x92/0x200 kernel/locking/rwsem.c:1577
       namespace_lock fs/namespace.c:1713 [inline]
       do_lock_mount+0x150/0x5b0 fs/namespace.c:2618
       lock_mount fs/namespace.c:2654 [inline]
       do_loopback fs/namespace.c:2777 [inline]
       path_mount+0xcda/0x1ea0 fs/namespace.c:3833
       do_mount fs/namespace.c:3852 [inline]
       __do_sys_mount fs/namespace.c:4062 [inline]
       __se_sys_mount fs/namespace.c:4039 [inline]
       __x64_sys_mount+0x284/0x310 fs/namespace.c:4039
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&sb->s_type->i_mutex_key#3){++++}-{3:3}:
       down_write+0x92/0x200 kernel/locking/rwsem.c:1577
       inode_lock include/linux/fs.h:815 [inline]
       start_creating.part.0+0xb2/0x370 fs/debugfs/inode.c:374
       start_creating fs/debugfs/inode.c:351 [inline]
       debugfs_create_dir+0x72/0x600 fs/debugfs/inode.c:593
       blk_register_queue+0x16a/0x4f0 block/blk-sysfs.c:766
       device_add_disk+0x77f/0x12f0 block/genhd.c:489
       add_disk include/linux/blkdev.h:741 [inline]
       brd_alloc.isra.0+0x57a/0x800 drivers/block/brd.c:401
       brd_init+0xf5/0x1e0 drivers/block/brd.c:481
       do_one_initcall+0x10e/0x6d0 init/main.c:1269
       do_initcall_level init/main.c:1331 [inline]
       do_initcalls init/main.c:1347 [inline]
       do_basic_setup init/main.c:1366 [inline]
       kernel_init_freeable+0x5ae/0x8a0 init/main.c:1580
       kernel_init+0x1e/0x2d0 init/main.c:1469
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #5 (&q->debugfs_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x147/0x930 kernel/locking/mutex.c:752
       blk_mq_init_sched+0x436/0x650 block/blk-mq-sched.c:473
       elevator_init_mq+0x2cc/0x420 block/elevator.c:610
       device_add_disk+0x10e/0x12f0 block/genhd.c:411
       sd_probe+0xa0e/0xf80 drivers/scsi/sd.c:4024
       call_driver_probe drivers/base/dd.c:579 [inline]
       really_probe+0x24f/0xa90 drivers/base/dd.c:658
       __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
       driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
       __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
       bus_for_each_drv+0x149/0x1d0 drivers/base/bus.c:459
       __device_attach_async_helper+0x1d1/0x290 drivers/base/dd.c:987
       async_run_entry_fn+0x9c/0x530 kernel/async.c:129
       process_one_work+0xa02/0x1bf0 kernel/workqueue.c:3232
       process_scheduled_works kernel/workqueue.c:3314 [inline]
       worker_thread+0x677/0xe90 kernel/workqueue.c:3395
       kthread+0x2c7/0x3b0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #4 (&q->q_usage_counter(queue)#51){++++}-{0:0}:
       blk_queue_enter+0x4d0/0x600 block/blk-core.c:328
       blk_mq_alloc_request+0x422/0x9c0 block/blk-mq.c:680
       scsi_alloc_request drivers/scsi/scsi_lib.c:1227 [inline]
       scsi_execute_cmd+0x1fe/0xf20 drivers/scsi/scsi_lib.c:304
       read_capacity_16+0x1f2/0xe60 drivers/scsi/sd.c:2655
       sd_read_capacity drivers/scsi/sd.c:2824 [inline]
       sd_revalidate_disk.isra.0+0x1989/0xa440 drivers/scsi/sd.c:3734
       sd_probe+0x887/0xf80 drivers/scsi/sd.c:4010
       call_driver_probe drivers/base/dd.c:579 [inline]
       really_probe+0x24f/0xa90 drivers/base/dd.c:658
       __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
       driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
       __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
       bus_for_each_drv+0x149/0x1d0 drivers/base/bus.c:459
       __device_attach_async_helper+0x1d1/0x290 drivers/base/dd.c:987
       async_run_entry_fn+0x9c/0x530 kernel/async.c:129
       process_one_work+0xa02/0x1bf0 kernel/workqueue.c:3232
       process_scheduled_works kernel/workqueue.c:3314 [inline]
       worker_thread+0x677/0xe90 kernel/workqueue.c:3395
       kthread+0x2c7/0x3b0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #3 (&q->limits_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x147/0x930 kernel/locking/mutex.c:752
       queue_limits_start_update include/linux/blkdev.h:935 [inline]
       loop_reconfigure_limits+0x1f2/0x960 drivers/block/loop.c:1004
       loop_set_block_size drivers/block/loop.c:1474 [inline]
       lo_simple_ioctl drivers/block/loop.c:1497 [inline]
       lo_ioctl+0xb92/0x1870 drivers/block/loop.c:1560
       blkdev_ioctl+0x27b/0x6c0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl fs/ioctl.c:893 [inline]
       __x64_sys_ioctl+0x19d/0x210 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#19){++++}-{0:0}:
       bio_queue_enter block/blk.h:76 [inline]
       blk_mq_submit_bio+0x2167/0x2b70 block/blk-mq.c:3090
       __submit_bio+0x399/0x630 block/blk-core.c:629
       __submit_bio_noacct_mq block/blk-core.c:716 [inline]
       submit_bio_noacct_nocheck+0x6c3/0xd00 block/blk-core.c:745
       submit_bio_noacct+0x57a/0x1fa0 block/blk-core.c:868
       xfs_buf_ioapply_map fs/xfs/xfs_buf.c:1585 [inline]
       _xfs_buf_ioapply+0x8a4/0xbe0 fs/xfs/xfs_buf.c:1673
       __xfs_buf_submit+0x241/0x840 fs/xfs/xfs_buf.c:1757
       xfs_buf_submit fs/xfs/xfs_buf.c:61 [inline]
       _xfs_buf_read fs/xfs/xfs_buf.c:808 [inline]
       xfs_buf_read_map+0x3e7/0xb40 fs/xfs/xfs_buf.c:872
       xfs_trans_read_buf_map+0x10a/0x9b0 fs/xfs/xfs_trans_buf.c:289
       xfs_trans_read_buf fs/xfs/xfs_trans.h:212 [inline]
       xfs_read_agf+0x2c1/0x5b0 fs/xfs/libxfs/xfs_alloc.c:3367
       xfs_alloc_read_agf+0x152/0xb90 fs/xfs/libxfs/xfs_alloc.c:3401
       xfs_alloc_fix_freelist+0x925/0xff0 fs/xfs/libxfs/xfs_alloc.c:2863
       xfs_alloc_vextent_prepare_ag+0x7c/0x6c0 fs/xfs/libxfs/xfs_alloc.c:3532
       xfs_alloc_vextent_iterate_ags.constprop.0+0x1b0/0x970 fs/xfs/libxfs/xfs_alloc.c:3717
       xfs_alloc_vextent_start_ag+0x32b/0x800 fs/xfs/libxfs/xfs_alloc.c:3806
       xfs_bmap_btalloc_best_length fs/xfs/libxfs/xfs_bmap.c:3731 [inline]
       xfs_bmap_btalloc+0xbc4/0x17d0 fs/xfs/libxfs/xfs_bmap.c:3776
       xfs_bmapi_allocate+0x23d/0xe80 fs/xfs/libxfs/xfs_bmap.c:4189
       xfs_bmapi_write+0x686/0xca0 fs/xfs/libxfs/xfs_bmap.c:4518
       xfs_dquot_disk_alloc+0x654/0xbb0 fs/xfs/xfs_dquot.c:376
       xfs_qm_dqread+0x55d/0x5f0 fs/xfs/xfs_dquot.c:715
       xfs_qm_dqget+0x142/0x470 fs/xfs/xfs_dquot.c:927
       xfs_qm_quotacheck_dqadjust+0xaa/0x570 fs/xfs/xfs_qm.c:1125
       xfs_qm_dqusage_adjust+0x511/0x680 fs/xfs/xfs_qm.c:1248
       xfs_iwalk_ag_recs+0x476/0x7c0 fs/xfs/xfs_iwalk.c:213
       xfs_iwalk_run_callbacks+0x1fa/0x560 fs/xfs/xfs_iwalk.c:371
       xfs_iwalk_ag+0x73a/0x940 fs/xfs/xfs_iwalk.c:477
       xfs_iwalk_ag_work+0x14e/0x1c0 fs/xfs/xfs_iwalk.c:619
       xfs_pwork_work+0x7f/0x160 fs/xfs/xfs_pwork.c:47
       process_one_work+0xa02/0x1bf0 kernel/workqueue.c:3232
       process_scheduled_works kernel/workqueue.c:3314 [inline]
       worker_thread+0x677/0xe90 kernel/workqueue.c:3395
       kthread+0x2c7/0x3b0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #1 (&xfs_nondir_ilock_class#3){++++}-{3:3}:
       down_write_nested+0x96/0x210 kernel/locking/rwsem.c:1693
       xfs_ilock+0x198/0x210 fs/xfs/xfs_inode.c:164
       xfs_reclaim_inode fs/xfs/xfs_icache.c:981 [inline]
       xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1675 [inline]
       xfs_icwalk_ag+0xa5e/0x17b0 fs/xfs/xfs_icache.c:1757
       xfs_icwalk fs/xfs/xfs_icache.c:1805 [inline]
       xfs_reclaim_inodes_nr+0x1bd/0x300 fs/xfs/xfs_icache.c:1047
       super_cache_scan+0x412/0x570 fs/super.c:227
       do_shrink_slab+0x44b/0x1190 mm/shrinker.c:437
       shrink_slab+0x332/0x12a0 mm/shrinker.c:664
       shrink_one+0x4ad/0x7c0 mm/vmscan.c:4835
       shrink_many mm/vmscan.c:4896 [inline]
       lru_gen_shrink_node mm/vmscan.c:4974 [inline]
       shrink_node+0x2420/0x3890 mm/vmscan.c:5954
       kswapd_shrink_node mm/vmscan.c:6782 [inline]
       balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6974
       kswapd+0x702/0xd50 mm/vmscan.c:7243
       kthread+0x2c7/0x3b0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x2425/0x3b90 kernel/locking/lockdep.c:5202
       lock_acquire.part.0+0x11b/0x370 kernel/locking/lockdep.c:5825
       __fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
       fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:3867
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4058 [inline]
       slab_alloc_node mm/slub.c:4136 [inline]
       __kmalloc_cache_noprof+0x4b/0x310 mm/slub.c:4312
       kmalloc_noprof include/linux/slab.h:878 [inline]
       get_mountpoint+0x14c/0x410 fs/namespace.c:909
       do_lock_mount+0x171/0x5b0 fs/namespace.c:2639
       lock_mount fs/namespace.c:2654 [inline]
       do_new_mount_fc fs/namespace.c:3449 [inline]
       do_new_mount fs/namespace.c:3514 [inline]
       path_mount+0x1695/0x1ea0 fs/namespace.c:3839
       do_mount fs/namespace.c:3852 [inline]
       __do_sys_mount fs/namespace.c:4062 [inline]
       __se_sys_mount fs/namespace.c:4039 [inline]
       __x64_sys_mount+0x284/0x310 fs/namespace.c:4039
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> &sb->s_type->i_mutex_key#3 --> namespace_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(namespace_sem);
                               lock(&sb->s_type->i_mutex_key#3);
                               lock(namespace_sem);
  lock(fs_reclaim);

 *** DEADLOCK ***

2 locks held by syz.6.1765/29153:
 #0: ffff888055a94158 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: inode_lock include/linux/fs.h:815 [inline]
 #0: ffff888055a94158 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: do_lock_mount+0xae/0x5b0 fs/namespace.c:2612
 #1: ffffffff8e1bfdd0 (namespace_sem){++++}-{3:3}, at: namespace_lock fs/namespace.c:1713 [inline]
 #1: ffffffff8e1bfdd0 (namespace_sem){++++}-{3:3}, at: do_lock_mount+0x150/0x5b0 fs/namespace.c:2618

stack backtrace:
CPU: 1 UID: 0 PID: 29153 Comm: syz.6.1765 Not tainted 6.12.24 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
 print_circular_bug+0x406/0x5c0 kernel/locking/lockdep.c:2074
 check_noncircular+0x2f7/0x3e0 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 kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x2425/0x3b90 kernel/locking/lockdep.c:5202
 lock_acquire.part.0+0x11b/0x370 kernel/locking/lockdep.c:5825
 __fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
 fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:3867
 might_alloc include/linux/sched/mm.h:318 [inline]
 slab_pre_alloc_hook mm/slub.c:4058 [inline]
 slab_alloc_node mm/slub.c:4136 [inline]
 __kmalloc_cache_noprof+0x4b/0x310 mm/slub.c:4312
 kmalloc_noprof include/linux/slab.h:878 [inline]
 get_mountpoint+0x14c/0x410 fs/namespace.c:909
 do_lock_mount+0x171/0x5b0 fs/namespace.c:2639
 lock_mount fs/namespace.c:2654 [inline]
 do_new_mount_fc fs/namespace.c:3449 [inline]
 do_new_mount fs/namespace.c:3514 [inline]
 path_mount+0x1695/0x1ea0 fs/namespace.c:3839
 do_mount fs/namespace.c:3852 [inline]
 __do_sys_mount fs/namespace.c:4062 [inline]
 __se_sys_mount fs/namespace.c:4039 [inline]
 __x64_sys_mount+0x284/0x310 fs/namespace.c:4039
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff6353ad5ad
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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:00007ff6361edf98 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ff6355e5fa0 RCX: 00007ff6353ad5ad
RDX: 00002000000000c0 RSI: 0000200000000080 RDI: 0000000000000000
RBP: 00007ff635446d56 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff6355e5fa0 R15: 00007ff6361ce000
 </TASK>

==================================================================

I hope it helps.
Best regards
Jianzhou Zhao

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2025-04-28 11:46 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2025-04-27  2:28 Potential Linux Crash: possible deadlock in do_lock_mount in linux6.12.24(longterm maintenance) Jianzhou Zhao
2025-04-28 11:46 ` Jan Kara

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