[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c.
[   42.002685] audit: type=1800 audit(1546626889.166:25): pid=7921 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0
[   42.033044] audit: type=1800 audit(1546626889.176:26): pid=7921 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0
[   42.076676] audit: type=1800 audit(1546626889.176:27): pid=7921 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 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.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   48.012791] sshd (8060) used greatest stack depth: 19848 bytes left
Warning: Permanently added '10.128.0.56' (ECDSA) to the list of known hosts.
executing program
executing program
[   54.754687] 
[   54.756367] ======================================================
[   54.762660] WARNING: possible circular locking dependency detected
[   54.768960] 4.20.0+ #9 Not tainted
[   54.772481] ------------------------------------------------------
[   54.778804] syz-executor253/8079 is trying to acquire lock:
[   54.784494] 00000000910fda11 (&mm->mmap_sem){++++}, at: __do_page_fault+0x9c2/0xd60
[   54.792302] 
[   54.792302] but task is already holding lock:
[   54.798262] 00000000191ab218 (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xe5/0x6a0
[   54.807868] 
[   54.807868] which lock already depends on the new lock.
[   54.807868] 
[   54.816156] 
[   54.816156] the existing dependency chain (in reverse order) is:
[   54.823748] 
[   54.823748] -> #2 (&sb->s_type->i_mutex_key#11){+.+.}:
[   54.830488]        down_write+0x8a/0x130
[   54.834531]        shmem_fallocate+0x168/0x1200
[   54.839181]        ashmem_shrink_scan+0x239/0x630
[   54.844005]        ashmem_ioctl+0x38a/0x12c0
[   54.848393]        do_vfs_ioctl+0x107b/0x17d0
[   54.852868]        ksys_ioctl+0xab/0xd0
[   54.856836]        __x64_sys_ioctl+0x73/0xb0
[   54.861226]        do_syscall_64+0x1a3/0x800
[   54.865627]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   54.871313] 
[   54.871313] -> #1 (ashmem_mutex){+.+.}:
[   54.876748]        __mutex_lock+0x12f/0x1670
[   54.881137]        mutex_lock_nested+0x16/0x20
[   54.885702]        ashmem_mmap+0x55/0x520
[   54.889832]        mmap_region+0xde5/0x1ca0
[   54.894132]        do_mmap+0xa09/0x1220
[   54.898090]        vm_mmap_pgoff+0x20b/0x2b0
[   54.902503]        ksys_mmap_pgoff+0x4f8/0x650
[   54.907069]        __x64_sys_mmap+0xe9/0x1b0
[   54.911458]        do_syscall_64+0x1a3/0x800
[   54.915846]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   54.921529] 
[   54.921529] -> #0 (&mm->mmap_sem){++++}:
[   54.927051]        lock_acquire+0x1db/0x570
[   54.931350]        down_read+0x8d/0x120
[   54.935313]        __do_page_fault+0x9c2/0xd60
[   54.939876]        do_page_fault+0xe6/0x7d8
[   54.944174]        page_fault+0x1e/0x30
[   54.948137]        iov_iter_fault_in_readable+0x377/0x450
[   54.953673]        generic_perform_write+0x202/0x6b0
[   54.958771]        __generic_file_write_iter+0x25e/0x630
[   54.964219]        generic_file_write_iter+0x34e/0x6a0
[   54.969499]        __vfs_write+0x764/0xb40
[   54.973725]        vfs_write+0x20c/0x580
[   54.977765]        ksys_write+0x105/0x260
[   54.981891]        __x64_sys_write+0x73/0xb0
[   54.986283]        do_syscall_64+0x1a3/0x800
[   54.990671]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   54.996355] 
[   54.996355] other info that might help us debug this:
[   54.996355] 
[   55.004466] Chain exists of:
[   55.004466]   &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#11
[   55.004466] 
[   55.015974]  Possible unsafe locking scenario:
[   55.015974] 
[   55.022019]        CPU0                    CPU1
[   55.026661]        ----                    ----
[   55.031300]   lock(&sb->s_type->i_mutex_key#11);
[   55.036033]                                lock(ashmem_mutex);
[   55.041991]                                lock(&sb->s_type->i_mutex_key#11);
[   55.049237]   lock(&mm->mmap_sem);
[   55.052751] 
[   55.052751]  *** DEADLOCK ***
[   55.052751] 
[   55.058785] 2 locks held by syz-executor253/8079:
[   55.063606]  #0: 0000000087f4e85c (sb_writers#5){.+.+}, at: vfs_write+0x429/0x580
[   55.071238]  #1: 00000000191ab218 (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xe5/0x6a0
[   55.081280] 
[   55.081280] stack backtrace:
[   55.085753] CPU: 1 PID: 8079 Comm: syz-executor253 Not tainted 4.20.0+ #9
[   55.092652] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   55.101981] Call Trace:
[   55.104549]  dump_stack+0x1db/0x2d0
[   55.108155]  ? dump_stack_print_info.cold+0x20/0x20
[   55.113151]  ? print_stack_trace+0x77/0xb0
[   55.117365]  ? vprintk_func+0x86/0x189
[   55.121235]  print_circular_bug.isra.0.cold+0x1cc/0x28f
[   55.126578]  __lock_acquire+0x3014/0x4a30
[   55.130717]  ? mark_held_locks+0x100/0x100
[   55.134954]  ? shmem_getpage_gfp+0x197e/0x4b70
[   55.139519]  ? trace_hardirqs_off_caller+0x300/0x300
[   55.144626]  ? do_raw_spin_trylock+0x270/0x270
[   55.149207]  ? shmem_getpage_gfp+0x26fb/0x4b70
[   55.153772]  ? __lock_is_held+0xb6/0x140
[   55.157818]  ? ip6gre_tunnel_lookup+0xf40/0x2170
[   55.162563]  lock_acquire+0x1db/0x570
[   55.166348]  ? __do_page_fault+0x9c2/0xd60
[   55.170564]  ? ___might_sleep+0x1e7/0x310
[   55.174700]  ? lock_release+0xc40/0xc40
[   55.178672]  ? __sanitizer_cov_trace_cmp8+0x18/0x20
[   55.183678]  ? cmp_ex_search+0x8c/0xb0
[   55.187550]  down_read+0x8d/0x120
[   55.190988]  ? __do_page_fault+0x9c2/0xd60
[   55.195208]  ? __down_interruptible+0x740/0x740
[   55.199863]  ? do_writepages+0x1a0/0x1a0
[   55.203904]  ? set_page_dirty+0x5dd/0xfc0
[   55.208037]  __do_page_fault+0x9c2/0xd60
[   55.212133]  do_page_fault+0xe6/0x7d8
[   55.215914]  ? unlock_page+0x2b1/0x4a0
[   55.219793]  ? vmalloc_sync_all+0x30/0x30
[   55.223955]  ? balance_dirty_pages_ratelimited+0x1b0/0x2370
[   55.229650]  ? copyin+0xd5/0x100
[   55.233000]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   55.237842]  page_fault+0x1e/0x30
[   55.241295] RIP: 0010:iov_iter_fault_in_readable+0x377/0x450
[   55.247099] Code: 89 f6 41 88 57 e0 e8 78 bd f3 fd 45 85 f6 74 c1 e9 70 fe ff ff e8 e9 bb f3 fd 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 45 bd f3 fd 85 db
[   55.265984] RSP: 0018:ffff8880a8a9f8a8 EFLAGS: 00010293
[   55.271323] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000020e1123f
[   55.278570] RDX: 0000000000000000 RSI: ffffffff838e3967 RDI: 0000000000000007
[   55.285840] RBP: ffff8880a8a9f948 R08: ffff888090fae180 R09: fffff94000415c8f
[   55.293091] R10: fffff94000415c8e R11: ffffea00020ae477 R12: 0000000000001000
[   55.300343] R13: 0000000000001000 R14: 0000000000000000 R15: ffff8880a8a9f920
[   55.307615]  ? iov_iter_fault_in_readable+0x367/0x450
[   55.312790]  ? iov_iter_fault_in_readable+0x367/0x450
[   55.317976]  ? copy_page_from_iter+0x900/0x900
[   55.322550]  ? shmem_write_begin+0x105/0x1e0
[   55.326957]  ? shmem_write_begin+0x10f/0x1e0
[   55.331365]  generic_perform_write+0x202/0x6b0
[   55.335940]  ? add_page_wait_queue+0x480/0x480
[   55.340501]  ? current_time+0x1b0/0x1b0
[   55.344455]  ? __sanitizer_cov_trace_cmp8+0x18/0x20
[   55.349490]  ? generic_write_check_limits+0x291/0x380
[   55.354664]  __generic_file_write_iter+0x25e/0x630
[   55.359575]  ? __fget+0x499/0x710
[   55.363012]  generic_file_write_iter+0x34e/0x6a0
[   55.367759]  ? __generic_file_write_iter+0x630/0x630
[   55.372845]  ? kfree+0xcf/0x230
[   55.376133]  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   55.381479]  ? __sanitizer_cov_trace_const_cmp8+0x18/0x20
[   55.386995]  ? iov_iter_init+0xea/0x220
[   55.390950]  __vfs_write+0x764/0xb40
[   55.394660]  ? kernel_read+0x120/0x120
[   55.398566]  ? rcu_read_lock_sched_held+0x110/0x130
[   55.403619]  ? rcu_sync_lockdep_assert+0x73/0xb0
[   55.408357]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[   55.413872]  ? __sb_start_write+0x1ac/0x360
[   55.418174]  vfs_write+0x20c/0x580
[   55.421697]  ksys_write+0x105/0x260
[   55.425306]  ? __ia32_sys_read+0xb0/0xb0
[   55.429370]  ? do_futex+0x2910/0x2910
[   55.433154]  ? trace_hardirqs_off_caller+0x300/0x300
[   55.438240]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[   55.442994]  __x64_sys_write+0x73/0xb0
[   55.446868]  do_syscall_64+0x1a3/0x800
[   55.450753]  ? syscall_return_slowpath+0x5f0/0x5f0
[   55.455831]  ? prepare_exit_to_usermode+0x232/0x3b0
[   55.460831]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   55.465679]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   55.470850] RIP: 0033:0x446399
[   55.474038] 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
[   55.492948] RSP: 002b:00007f184f34bda8 EFLAGS: 00000297 ORIG_RAX: 0000000000000001
[   55.500635] RAX: ffffffffffffffda RBX: 00000000006dcc28 RCX: 0000000000446399
executing program
[   55.507883] RDX: 00000000fffffe48 RSI: 0000000020004240 RDI: 0000000000000004
[   55.515133] RBP: 00000000006dcc20 R08: 0000000000000000 R09: 0000000000000000
[   55.522380] R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dcc2c
[   55.529641] R13: 656363615f6c6361 R14: 5f7869736f70275b R15: 00000000006dcd2c
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