[   34.920552] audit: type=1800 audit(1549173511.028:27): pid=7450 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0
[   34.920572] audit: type=1800 audit(1549173511.028:28): pid=7450 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="ssh" dev="sda1" ino=2417 res=0
[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c.
[   35.987048] audit: type=1800 audit(1549173512.118:29): pid=7450 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0
[   36.005742] audit: type=1800 audit(1549173512.118:30): pid=7450 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0

Debian GNU/Linux 7 syzkaller ttyS0

Warning: Permanently added '10.128.0.173' (ECDSA) to the list of known hosts.
executing program
syzkaller login: [   48.214819] 
[   48.216487] ======================================================
[   48.222785] WARNING: possible circular locking dependency detected
[   48.229083] 5.0.0-rc4+ #58 Not tainted
[   48.232954] ------------------------------------------------------
[   48.239252] syz-executor778/7604 is trying to acquire lock:
[   48.245025] 000000003159e26f (&mm->mmap_sem){++++}, at: __do_page_fault+0x9c2/0xd60
[   48.252811] 
[   48.252811] but task is already holding lock:
[   48.258867] 0000000030cdf7e0 (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xdf/0x610
[   48.268506] 
[   48.268506] which lock already depends on the new lock.
[   48.268506] 
[   48.276804] 
[   48.276804] the existing dependency chain (in reverse order) is:
[   48.284458] 
[   48.284458] -> #2 (&sb->s_type->i_mutex_key#11){+.+.}:
[   48.291221]        down_write+0x38/0x90
[   48.295185]        shmem_fallocate+0x15a/0xc60
[   48.299942]        ashmem_shrink_scan+0x1d7/0x4f0
[   48.305920]        ashmem_ioctl+0x2f0/0x11a0
[   48.310313]        do_vfs_ioctl+0xd6e/0x1390
[   48.315389]        ksys_ioctl+0xab/0xd0
[   48.319465]        __x64_sys_ioctl+0x73/0xb0
[   48.323856]        do_syscall_64+0x103/0x610
[   48.328245]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   48.333929] 
[   48.333929] -> #1 (ashmem_mutex){+.+.}:
[   48.339366]        __mutex_lock+0xf7/0x1310
[   48.343751]        mutex_lock_nested+0x16/0x20
[   48.348388]        ashmem_mmap+0x55/0x520
[   48.352536]        mmap_region+0xc37/0x1760
[   48.356836]        do_mmap+0x8e2/0x1080
[   48.360793]        vm_mmap_pgoff+0x1c5/0x230
[   48.365188]        ksys_mmap_pgoff+0x4aa/0x630
[   48.369751]        __x64_sys_mmap+0xe9/0x1b0
[   48.374142]        do_syscall_64+0x103/0x610
[   48.378530]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   48.384213] 
[   48.384213] -> #0 (&mm->mmap_sem){++++}:
[   48.389740]        lock_acquire+0x16f/0x3f0
[   48.394044]        down_read+0x3b/0x90
[   48.397915]        __do_page_fault+0x9c2/0xd60
[   48.402476]        do_page_fault+0x71/0x581
[   48.406776]        page_fault+0x1e/0x30
[   48.410733]        iov_iter_fault_in_readable+0x377/0x450
[   48.416249]        generic_perform_write+0x195/0x530
[   48.421554]        __generic_file_write_iter+0x25e/0x630
[   48.426995]        generic_file_write_iter+0x360/0x610
[   48.432255]        __vfs_write+0x613/0x8e0
[   48.436470]        vfs_write+0x20c/0x580
[   48.440520]        ksys_write+0xea/0x1f0
[   48.444575]        __x64_sys_write+0x73/0xb0
[   48.448968]        do_syscall_64+0x103/0x610
[   48.453364]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   48.459053] 
[   48.459053] other info that might help us debug this:
[   48.459053] 
[   48.467167] Chain exists of:
[   48.467167]   &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#11
[   48.467167] 
[   48.478677]  Possible unsafe locking scenario:
[   48.478677] 
[   48.484711]        CPU0                    CPU1
[   48.489352]        ----                    ----
[   48.493995]   lock(&sb->s_type->i_mutex_key#11);
[   48.498730]                                lock(ashmem_mutex);
[   48.504764]                                lock(&sb->s_type->i_mutex_key#11);
[   48.512022]   lock(&mm->mmap_sem);
[   48.515750] 
[   48.515750]  *** DEADLOCK ***
[   48.515750] 
[   48.521861] 2 locks held by syz-executor778/7604:
[   48.526685]  #0: 00000000a4aa1c47 (sb_writers#5){.+.+}, at: vfs_write+0x429/0x580
[   48.534297]  #1: 0000000030cdf7e0 (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xdf/0x610
[   48.544336] 
[   48.544336] stack backtrace:
[   48.548818] CPU: 0 PID: 7604 Comm: syz-executor778 Not tainted 5.0.0-rc4+ #58
[   48.556068] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   48.565414] Call Trace:
[   48.568037]  dump_stack+0x172/0x1f0
[   48.571657]  print_circular_bug.isra.0.cold+0x1cc/0x28f
[   48.577009]  __lock_acquire+0x2f00/0x4700
[   48.581139]  ? free_unref_page_list+0x86f/0xc40
[   48.585798]  ? release_pages+0x60d/0x1940
[   48.589927]  ? free_unref_page_list+0x86f/0xc40
[   48.594585]  ? mark_held_locks+0x100/0x100
[   48.598804]  ? mark_held_locks+0x100/0x100
[   48.603022]  ? __lock_is_held+0xb6/0x140
[   48.607078]  lock_acquire+0x16f/0x3f0
[   48.610865]  ? __do_page_fault+0x9c2/0xd60
[   48.615088]  down_read+0x3b/0x90
[   48.618436]  ? __do_page_fault+0x9c2/0xd60
[   48.622651]  __do_page_fault+0x9c2/0xd60
[   48.626778]  do_page_fault+0x71/0x581
[   48.630572]  page_fault+0x1e/0x30
[   48.634010] RIP: 0010:iov_iter_fault_in_readable+0x377/0x450
[   48.639788] Code: 89 f6 41 88 57 e0 e8 b8 2b 47 fe 45 85 f6 74 c1 e9 70 fe ff ff e8 29 2a 47 fe 0f 1f 00 0f ae e8 44 89 f0 48 8b 8d 68 ff ff ff <8a> 11 89 c3 0f 1f 00 41 88 57 d0 31 ff 89 de e8 85 2b 47 fe 85 db
[   48.658671] RSP: 0018:ffff888093bc79b8 EFLAGS: 00010293
[   48.664074] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000020e8953f
[   48.671330] RDX: 0000000000000000 RSI: ffffffff8328b1e7 RDI: 0000000000000007
[   48.678584] RBP: ffff888093bc7a58 R08: ffff8880973664c0 R09: fffff94000417e9f
[   48.685842] R10: fffff94000417e9e R11: ffffea00020bf4f7 R12: 0000000000001000
[   48.693106] R13: 0000000000001000 R14: 0000000000000000 R15: ffff888093bc7a30
[   48.700378]  ? iov_iter_fault_in_readable+0x367/0x450
[   48.705565]  ? iov_iter_fault_in_readable+0x367/0x450
[   48.710737]  ? copy_page_from_iter+0x750/0x750
[   48.715415]  generic_perform_write+0x195/0x530
[   48.719982]  ? page_endio+0x780/0x780
[   48.723770]  ? current_time+0x140/0x140
[   48.727729]  ? lock_acquire+0x16f/0x3f0
[   48.731687]  __generic_file_write_iter+0x25e/0x630
[   48.736601]  ? __sanitizer_cov_trace_cmp8+0x18/0x20
[   48.741614]  generic_file_write_iter+0x360/0x610
[   48.746359]  ? __generic_file_write_iter+0x630/0x630
[   48.751464]  ? __fget+0x340/0x540
[   48.754905]  ? __sanitizer_cov_trace_const_cmp8+0x18/0x20
[   48.760547]  ? iov_iter_init+0xea/0x220
[   48.764515]  __vfs_write+0x613/0x8e0
[   48.768224]  ? kernel_read+0x120/0x120
[   48.772106]  ? rcu_read_lock_sched_held+0x110/0x130
[   48.777118]  ? rcu_sync_lockdep_assert+0x73/0xb0
[   48.781862]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[   48.787398]  ? __sb_start_write+0x1ac/0x360
[   48.791705]  vfs_write+0x20c/0x580
[   48.795226]  ksys_write+0xea/0x1f0
[   48.798748]  ? __ia32_sys_read+0xb0/0xb0
[   48.802796]  ? do_syscall_64+0x26/0x610
[   48.806750]  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   48.812091]  ? do_syscall_64+0x26/0x610
[   48.816044]  __x64_sys_write+0x73/0xb0
[   48.819912]  do_syscall_64+0x103/0x610
[   48.823784]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   48.828952] RIP: 0033:0x4463e9
[   48.832134] Code: e8 2c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
[   48.851019] RSP: 002b:00007ff749ea4da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[   48.858715] RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 00000000004463e9
executing program
[   48.865973] RDX: 00000000fffffda2 RSI: 0000000020000540 RDI: 0000000000000004
[   48.873290] RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
[   48.880543] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
[   48.888317] R13: 0000000000000000 R14: 0080000080000000 R15: 20c49ba5e353f7cf
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