On 25/7/21 8:39 pm, syzbot wrote:

Hello,

syzbot found the following issue on:

HEAD commit: f0fddcec6b62 Merge tag 'for-5.14-rc2-tag' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13cbb70e300000 kernel config: https://syzkaller.appspot.com/x/.config?x=5dc0e3202ae2f574 dashboard link: https://syzkaller.appspot.com/bug?extid=17c16b868e6af41acdd4 compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17667ecc300000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=179e0582300000

The issue was bisected to:

commit e918188611f073063415f40fae568fa4d86d9044 Author: Boqun Feng boqun.feng@gmail.com Date: Fri Aug 7 07:42:20 2020 +0000

 locking: More accurate annotations for read_lock()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=109610b2300000 final oops: https://syzkaller.appspot.com/x/report.txt?x=129610b2300000 console output: https://syzkaller.appspot.com/x/log.txt?x=149610b2300000

IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+17c16b868e6af41acdd4@syzkaller.appspotmail.com Fixes: e918188611f0 ("locking: More accurate annotations for read_lock()")

======================================================== WARNING: possible irq lock inversion dependency detected 5.14.0-rc2-syzkaller #0 Not tainted

---

syz-executor065/8431 just changed the state of lock: ffff888027e94148 (&timer->lock){..-.}-{2:2}, at: snd_timer_interrupt+0x210/0x1410 sound/core/timer.c:857 but this lock took another, SOFTIRQ-READ-unsafe lock in the past: (&f->f_owner.lock){.+.+}-{2:2}

and interrupts could create inverse lock ordering between them.

other info that might help us debug this: Chain exists of: &timer->lock --> &new->fa_lock --> &f->f_owner.lock

Possible interrupt unsafe locking scenario:

    CPU0                    CPU1
    ----                    ----

lock(&f->f_owner.lock); local_irq_disable(); lock(&timer->lock); lock(&new->fa_lock);

<Interrupt> lock(&timer->lock);

*** DEADLOCK ***

4 locks held by syz-executor065/8431: #0: ffff888029390460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:375 #1: ffff888039f60e80 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:809 [inline] #1: ffff888039f60e80 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: filename_create+0x19f/0x700 fs/namei.c:3602 #2: ffffffff8c7177c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:266 #3: ffffc90000dc0be0 ((&priv->tlist)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline] #3: ffffc90000dc0be0 ((&priv->tlist)){+.-.}-{0:0}, at: call_timer_fn+0xbd/0x210 kernel/time/timer.c:1407

the shortest dependencies between 2nd lock and 1st lock: -> (&f->f_owner.lock){.+.+}-{2:2} { HARDIRQ-ON-R at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:223 f_getown_ex fs/fcntl.c:211 [inline] do_fcntl+0x150/0x1510 fs/fcntl.c:395 __do_sys_fcntl fs/fcntl.c:471 [inline] __se_sys_fcntl+0xd8/0x1b0 fs/fcntl.c:456 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae SOFTIRQ-ON-R at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:223 f_getown_ex fs/fcntl.c:211 [inline] do_fcntl+0x150/0x1510 fs/fcntl.c:395 __do_sys_fcntl fs/fcntl.c:471 [inline] __se_sys_fcntl+0xd8/0x1b0 fs/fcntl.c:456 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae INITIAL READ USE at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:159 [inline] _raw_read_lock_irqsave+0xbb/0x100 kernel/locking/spinlock.c:231 send_sigio+0x2f/0x300 fs/fcntl.c:795 kill_fasync_rcu fs/fcntl.c:1019 [inline] kill_fasync+0x1e3/0x430 fs/fcntl.c:1033 snd_timer_user_ccallback+0x3ee/0x710 sound/core/timer.c:1387 snd_timer_notify1+0x19e/0x340 sound/core/timer.c:516 snd_timer_start1+0x53d/0x640 sound/core/timer.c:578 snd_timer_start sound/core/timer.c:697 [inline] snd_timer_user_start sound/core/timer.c:1985 [inline] __snd_timer_user_ioctl+0xe18/0x5ed0 sound/core/timer.c:2108 snd_timer_user_ioctl+0x5d/0x80 sound/core/timer.c:2129 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae } ... key at: [<ffffffff907d04a0>] __alloc_file.__key+0x0/0x10 ... acquired at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:159 [inline] _raw_read_lock_irqsave+0xbb/0x100 kernel/locking/spinlock.c:231 send_sigio+0x2f/0x300 fs/fcntl.c:795 kill_fasync_rcu fs/fcntl.c:1019 [inline] kill_fasync+0x1e3/0x430 fs/fcntl.c:1033 snd_timer_user_ccallback+0x3ee/0x710 sound/core/timer.c:1387 snd_timer_notify1+0x19e/0x340 sound/core/timer.c:516 snd_timer_start1+0x53d/0x640 sound/core/timer.c:578 snd_timer_start sound/core/timer.c:697 [inline] snd_timer_user_start sound/core/timer.c:1985 [inline] __snd_timer_user_ioctl+0xe18/0x5ed0 sound/core/timer.c:2108 snd_timer_user_ioctl+0x5d/0x80 sound/core/timer.c:2129 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

-> (&new->fa_lock){....}-{2:2} { INITIAL USE at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_write_lock_irq include/linux/rwlock_api_smp.h:196 [inline] _raw_write_lock_irq+0xae/0xf0 kernel/locking/spinlock.c:311 fasync_remove_entry+0xff/0x1d0 fs/fcntl.c:890 __fput+0x65b/0x7b0 fs/file_table.c:277 task_work_run+0x146/0x1c0 kernel/task_work.c:164 exit_task_work include/linux/task_work.h:32 [inline] do_exit+0x72b/0x2510 kernel/exit.c:825 do_group_exit+0x168/0x2d0 kernel/exit.c:922 get_signal+0x16b0/0x2080 kernel/signal.c:2808 arch_do_signal_or_restart+0x8e/0x6d0 arch/x86/kernel/signal.c:865 handle_signal_work kernel/entry/common.c:148 [inline] exit_to_user_mode_loop kernel/entry/common.c:172 [inline] exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:209 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x26/0x60 kernel/entry/common.c:302 do_syscall_64+0x4c/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae INITIAL READ USE at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:223 kill_fasync_rcu fs/fcntl.c:1012 [inline] kill_fasync+0x13b/0x430 fs/fcntl.c:1033 snd_timer_user_ccallback+0x3ee/0x710 sound/core/timer.c:1387 snd_timer_notify1+0x19e/0x340 sound/core/timer.c:516 snd_timer_start1+0x53d/0x640 sound/core/timer.c:578 snd_timer_start sound/core/timer.c:697 [inline] snd_timer_user_start sound/core/timer.c:1985 [inline] __snd_timer_user_ioctl+0xe18/0x5ed0 sound/core/timer.c:2108 snd_timer_user_ioctl+0x5d/0x80 sound/core/timer.c:2129 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae } ... key at: [<ffffffff907d1360>] fasync_insert_entry.__key+0x0/0x40 ... acquired at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:223 kill_fasync_rcu fs/fcntl.c:1012 [inline] kill_fasync+0x13b/0x430 fs/fcntl.c:1033 snd_timer_user_ccallback+0x3ee/0x710 sound/core/timer.c:1387 snd_timer_notify1+0x19e/0x340 sound/core/timer.c:516 snd_timer_start1+0x53d/0x640 sound/core/timer.c:578 snd_timer_start sound/core/timer.c:697 [inline] snd_timer_user_start sound/core/timer.c:1985 [inline] __snd_timer_user_ioctl+0xe18/0x5ed0 sound/core/timer.c:2108 snd_timer_user_ioctl+0x5d/0x80 sound/core/timer.c:2129 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

-> (&timer->lock){..-.}-{2:2} { IN-SOFTIRQ-W at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:159 snd_timer_interrupt+0x210/0x1410 sound/core/timer.c:857 call_timer_fn+0xf6/0x210 kernel/time/timer.c:1417 expire_timers kernel/time/timer.c:1462 [inline] __run_timers+0x6ff/0x910 kernel/time/timer.c:1731 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1744 __do_softirq+0x372/0x783 kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x21b/0x260 kernel/softirq.c:636 irq_exit_rcu+0x5/0x20 kernel/softirq.c:648 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 __preempt_count_add arch/x86/include/asm/preempt.h:80 [inline] rcu_is_watching+0xd/0xb0 kernel/rcu/tree.c:1159 rcu_read_lock include/linux/rcupdate.h:688 [inline] get_cached_acl+0x103/0x540 fs/posix_acl.c:44 get_acl+0x20/0x2e0 fs/posix_acl.c:108 posix_acl_create+0x119/0x560 fs/posix_acl.c:616 ext4_init_acl+0xa6/0x3d0 fs/ext4/acl.c:282 __ext4_new_inode+0x44e7/0x5810 fs/ext4/ialloc.c:1316 ext4_mkdir+0x3fa/0xc10 fs/ext4/namei.c:2921 vfs_mkdir+0x451/0x630 fs/namei.c:3823 do_mkdirat+0x267/0x3e0 fs/namei.c:3848 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae INITIAL USE at: lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:159 snd_timer_resolution sound/core/timer.c:489 [inline] snd_timer_user_params sound/core/timer.c:1852 [inline] __snd_timer_user_ioctl+0x1df7/0x5ed0 sound/core/timer.c:2101 snd_timer_user_ioctl+0x5d/0x80 sound/core/timer.c:2129 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae } ... key at: [<ffffffff90b60220>] snd_timer_new.__key+0x0/0x40 ... acquired at: mark_usage kernel/locking/lockdep.c:4488 [inline] __lock_acquire+0xca1/0x6100 kernel/locking/lockdep.c:4969 lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:159 snd_timer_interrupt+0x210/0x1410 sound/core/timer.c:857 call_timer_fn+0xf6/0x210 kernel/time/timer.c:1417 expire_timers kernel/time/timer.c:1462 [inline] __run_timers+0x6ff/0x910 kernel/time/timer.c:1731 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1744 __do_softirq+0x372/0x783 kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x21b/0x260 kernel/softirq.c:636 irq_exit_rcu+0x5/0x20 kernel/softirq.c:648 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 __preempt_count_add arch/x86/include/asm/preempt.h:80 [inline] rcu_is_watching+0xd/0xb0 kernel/rcu/tree.c:1159 rcu_read_lock include/linux/rcupdate.h:688 [inline] get_cached_acl+0x103/0x540 fs/posix_acl.c:44 get_acl+0x20/0x2e0 fs/posix_acl.c:108 posix_acl_create+0x119/0x560 fs/posix_acl.c:616 ext4_init_acl+0xa6/0x3d0 fs/ext4/acl.c:282 __ext4_new_inode+0x44e7/0x5810 fs/ext4/ialloc.c:1316 ext4_mkdir+0x3fa/0xc10 fs/ext4/namei.c:2921 vfs_mkdir+0x451/0x630 fs/namei.c:3823 do_mkdirat+0x267/0x3e0 fs/namei.c:3848 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

stack backtrace: CPU: 1 PID: 8431 Comm: syz-executor065 Not tainted 5.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace:

<IRQ> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105 print_irq_inversion_bug+0xa58/0xda0 kernel/locking/lockdep.c:4000 check_usage_forwards kernel/locking/lockdep.c:2585 [inline] mark_lock_irq kernel/locking/lockdep.c:4163 [inline] mark_lock+0x1064/0x1eb0 kernel/locking/lockdep.c:4593 mark_usage kernel/locking/lockdep.c:4488 [inline] __lock_acquire+0xca1/0x6100 kernel/locking/lockdep.c:4969 lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:159 snd_timer_interrupt+0x210/0x1410 sound/core/timer.c:857 call_timer_fn+0xf6/0x210 kernel/time/timer.c:1417 expire_timers kernel/time/timer.c:1462 [inline] __run_timers+0x6ff/0x910 kernel/time/timer.c:1731 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1744 __do_softirq+0x372/0x783 kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x21b/0x260 kernel/softirq.c:636 irq_exit_rcu+0x5/0x20 kernel/softirq.c:648 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100 </IRQ> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 RIP: 0010:rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:339 [inline] RIP: 0010:rcu_is_watching+0xd/0xb0 kernel/rcu/tree.c:1160 Code: 41 5e 41 5f 5d c3 e8 92 a8 6d 08 41 f7 c4 00 02 00 00 75 b6 eb b5 e8 62 a8 6d 08 66 90 41 57 41 56 53 65 83 05 4b e3 96 7e 01 <e8> 1e bb 6d 08 89 c3 83 f8 08 73 74 49 bf 00 00 00 00 00 fc ff df RSP: 0018:ffffc9000164f820 EFLAGS: 00000282 RAX: 12a9aafecb760900 RBX: 1ffff920002c9f0c RCX: ffffffff816213c5 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc9000164f8e8 R08: dffffc0000000000 R09: fffffbfff1f5e1b1 R10: fffffbfff1f5e1b1 R11: 0000000000000000 R12: 0000000000004000 R13: dffffc0000000000 R14: 1ffff920002c9f10 R15: ffff888039f60d48 rcu_read_lock include/linux/rcupdate.h:688 [inline] get_cached_acl+0x103/0x540 fs/posix_acl.c:44 get_acl+0x20/0x2e0 fs/posix_acl.c:108 posix_acl_create+0x119/0x560 fs/posix_acl.c:616 ext4_init_acl+0xa6/0x3d0 fs/ext4/acl.c:282 __ext4_new_inode+0x44e7/0x5810 fs/ext4/ialloc.c:1316 ext4_mkdir+0x3fa/0xc10 fs/ext4/namei.c:2921 vfs_mkdir+0x451/0x630 fs/namei.c:3823 do_mkdirat+0x267/0x3e0 fs/namei.c:3848 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x445d87 Code: 73 01 c3 48 c7 c1 bc 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 53 00 00 00 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:00007ffc332de6a8 EFLAGS: 00000202 ORIG_RAX: 0000000000000053 RAX: ffffffffffffffda RBX: 000000000000e3bb RCX: 0000000000445d87 RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007ffc332de740 RBP: 0000000000002ebc R08: 0000000000000000 R09: 0000000000000005 R10: 00007ffc332de445 R11: 0000000000000202 R12: 00007ffc332de6e4 R13: 00007ffc332de740 R14: 00000000000000bd R15: 431bde82d7b634db

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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@googlegroups.com.

syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches

#syz fix: fcntl: fix potential deadlocks for &fown_struct.lock

This deadlock has the same root cause, and thus the same fix [1], as "possible deadlock in do_fcntl" [2].

[1]: https://lore.kernel.org/lkml/20210702091831.615042-2-desmondcheongzx@gmail.c... [2]: https://syzkaller.appspot.com/bug?id=923cfc6c6348963f99886a0176ef11dcc429547...

Best, Desmond