[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[    9.277638] random: sshd: uninitialized urandom read (32 bytes read)
[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   17.172975] random: sshd: uninitialized urandom read (32 bytes read)
[   17.403155] random: sshd: uninitialized urandom read (32 bytes read)
[   17.539904] random: crng init done
Warning: Permanently added '10.128.0.56' (ECDSA) to the list of known hosts.
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[   35.418597] hrtimer: interrupt took 25792 ns
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[   35.962289] 
[   35.964097] ======================================================
[   35.970500] [ INFO: possible circular locking dependency detected ]
[   35.977150] 4.9.190+ #5 Not tainted
[   35.980870] -------------------------------------------------------
[   35.988062] syz-executor534/2086 is trying to acquire lock:
[   35.993759]  (&mm->mmap_sem){++++++}, at: [<000000002bcfb8bc>] __do_page_fault+0x7bd/0xa60

[   36.002650] but task is already holding lock:
[   36.007307]  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000e5dcf918>] generic_file_write_iter+0x9a/0x630

[   36.018057] which lock already depends on the new lock.
[   36.018057] 
[   36.025058] 
[   36.025058] the existing dependency chain (in reverse order) is:
[   36.032677] 
-> #2 (&sb->s_type->i_mutex_key#10){+.+.+.}:
[   36.038954]        lock_acquire+0x133/0x3d0
[   36.043270]        down_write+0x41/0xa0
[   36.047234]        shmem_fallocate+0x143/0xab0
[   36.051816]        ashmem_shrink_scan+0x1c3/0x4c0
[   36.056648]        ashmem_ioctl+0x29b/0xdd0
[   36.061003]        do_vfs_ioctl+0xb87/0x11d0
[   36.065405]        SyS_ioctl+0x8f/0xc0
[   36.069282]        do_syscall_64+0x1ad/0x5c0
[   36.073681]        entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   36.079286] 
-> #1 (ashmem_mutex){+.+.+.}:
[   36.084124]        lock_acquire+0x133/0x3d0
[   36.088431]        mutex_lock_nested+0xc7/0x920
[   36.093087]        ashmem_mmap+0x53/0x470
[   36.097224]        mmap_region+0x7e7/0xfa0
[   36.101444]        do_mmap+0x539/0xbc0
[   36.105320]        vm_mmap_pgoff+0x179/0x1c0
[   36.109714]        SyS_mmap_pgoff+0xfa/0x1b0
[   36.114113]        SyS_mmap+0x16/0x20
[   36.117897]        do_syscall_64+0x1ad/0x5c0
[   36.122296]        entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   36.127902] 
-> #0 (&mm->mmap_sem){++++++}:
[   36.132841]        __lock_acquire+0x2d22/0x4390
[   36.137494]        lock_acquire+0x133/0x3d0
[   36.141799]        down_read+0x44/0xb0
[   36.145670]        __do_page_fault+0x7bd/0xa60
[   36.150247]        do_page_fault+0x28/0x30
[   36.154467]        page_fault+0x25/0x30
[   36.158426]        generic_perform_write+0x1b6/0x500
[   36.163513]        __generic_file_write_iter+0x340/0x530
[   36.168946]        generic_file_write_iter+0x38a/0x630
[   36.174208]        __vfs_write+0x3c1/0x560
[   36.178425]        vfs_write+0x185/0x520
[   36.182472]        SyS_write+0x121/0x270
[   36.186525]        do_syscall_64+0x1ad/0x5c0
[   36.190926]        entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   36.196530] 
[   36.196530] other info that might help us debug this:
[   36.196530] 
[   36.204655] Chain exists of:
  &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#10

[   36.214509]  Possible unsafe locking scenario:
[   36.214509] 
[   36.220551]        CPU0                    CPU1
[   36.225200]        ----                    ----
[   36.229850]   lock(&sb->s_type->i_mutex_key#10);
[   36.234981]                                lock(ashmem_mutex);
[   36.241196]                                lock(&sb->s_type->i_mutex_key#10);
[   36.248846]   lock(&mm->mmap_sem);
[   36.252630] 
[   36.252630]  *** DEADLOCK ***
[   36.252630] 
[   36.258674] 2 locks held by syz-executor534/2086:
[   36.263505]  #0:  (sb_writers#6){.+.+.+}, at: [<000000003f868c80>] vfs_write+0x3e9/0x520
[   36.272413]  #1:  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000e5dcf918>] generic_file_write_iter+0x9a/0x630
[   36.283722] 
[   36.283722] stack backtrace:
[   36.288207] CPU: 1 PID: 2086 Comm: syz-executor534 Not tainted 4.9.190+ #5
[   36.295211]  ffff8801ced0f5d8 ffffffff81b65c51 ffffffff83caf440 ffffffff83cb8dd0
[   36.303253]  ffffffff83ccccc0 ffffffff84250fc0 ffff8801cf2b97c0 ffff8801ced0f630
[   36.311288]  ffffffff814069f3 dffffc0000000000 ffffffff84029bc0 ffff8801cf2ba0c0
[   36.319327] Call Trace:
[   36.321906]  [<0000000024ac8c2e>] dump_stack+0xc1/0x120
[   36.327266]  [<000000007767f001>] print_circular_bug.cold+0x2f6/0x454
[   36.333832]  [<0000000066084f99>] __lock_acquire+0x2d22/0x4390
[   36.339792]  [<00000000f88274e9>] ? kasan_unpoison_shadow+0x35/0x50
[   36.346189]  [<00000000d1e702b9>] ? kasan_alloc_pages+0x38/0x40
[   36.352234]  [<00000000e9e7ed19>] ? trace_hardirqs_on+0x10/0x10
[   36.358282]  [<000000008fc496cd>] ? trace_hardirqs_on_caller+0x385/0x5a0
[   36.365112]  [<000000002f3b89d5>] ? trace_hardirqs_on_thunk+0x1a/0x1c
[   36.371682]  [<00000000194c6423>] ? check_preemption_disabled+0x3c/0x200
[   36.378506]  [<000000001e85c3ae>] lock_acquire+0x133/0x3d0
[   36.384119]  [<000000002bcfb8bc>] ? __do_page_fault+0x7bd/0xa60
[   36.390166]  [<00000000c8812813>] down_read+0x44/0xb0
[   36.395347]  [<000000002bcfb8bc>] ? __do_page_fault+0x7bd/0xa60
[   36.401395]  [<000000002bcfb8bc>] __do_page_fault+0x7bd/0xa60
[   36.407279]  [<0000000017032c64>] ? debug_lockdep_rcu_enabled+0x71/0xa0
[   36.414195]  [<00000000bcf882c6>] ? bad_area_access_error+0x3d0/0x3d0
[   36.420770]  [<000000009db0942d>] ? trace_hardirqs_off_thunk+0x1a/0x1c
[   36.427427]  [<0000000006c7666f>] do_page_fault+0x28/0x30
[   36.432950]  [<000000006dd33d96>] page_fault+0x25/0x30
[   36.438218]  [<00000000f4d522ed>] ? iov_iter_fault_in_readable+0x300/0x3d0
[   36.445221]  [<0000000015f93eaa>] ? iov_iter_fault_in_readable+0x30d/0x3d0
[   36.452219]  [<00000000f4d522ed>] ? iov_iter_fault_in_readable+0x300/0x3d0
[   36.459221]  [<00000000174d458d>] ? iov_iter_init+0x1d0/0x1d0
[   36.465097]  [<00000000cc068bea>] generic_perform_write+0x1b6/0x500
[   36.471492]  [<000000007295c419>] ? filemap_page_mkwrite+0x280/0x280
[   36.477973]  [<0000000029b6c34f>] ? current_time+0xd0/0xd0
[   36.483584]  [<00000000f940ce63>] __generic_file_write_iter+0x340/0x530
[   36.490323]  [<00000000103d1f22>] generic_file_write_iter+0x38a/0x630
[   36.496892]  [<00000000f36b52b3>] __vfs_write+0x3c1/0x560
[   36.502414]  [<00000000b63a806c>] ? bpf_fd_pass+0x270/0x270
[   36.508115]  [<0000000007f05c6b>] ? __vfs_read+0x550/0x550
[   36.513727]  [<00000000951d8537>] ? rcu_read_lock_sched_held+0x10b/0x130
[   36.520556]  [<00000000723f321b>] ? rcu_sync_lockdep_assert+0x73/0xb0
[   36.527120]  [<0000000049d2050d>] ? __sb_start_write+0x161/0x310
[   36.533250]  [<00000000bef1e415>] vfs_write+0x185/0x520
[   36.538602]  [<0000000001d6d3d2>] SyS_write+0x121/0x270
[   36.543954]  [<000000009806e3a5>] ? SyS_read+0x270/0x270
[   36.549395]  [<00000000fb582d51>] ? do_syscall_64+0x4a/0x5c0
[   36.555178]  [<000000009806e3a5>] ? SyS_read+0x270/0x270
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[   36.560612]  [<0000000069256ca3>] do_syscall_64+0x1ad/0x5c0
[   36.566591]  [<00000000e706def4>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
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