[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.282025] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [ 21.462280] random: sshd: uninitialized urandom read (32 bytes read, 36 bits of entropy available) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.834138] random: sshd: uninitialized urandom read (32 bytes read, 36 bits of entropy available) [ 22.791154] random: sshd: uninitialized urandom read (32 bytes read, 107 bits of entropy available) [ 22.967605] random: sshd: uninitialized urandom read (32 bytes read, 113 bits of entropy available) Warning: Permanently added '10.128.0.60' (ECDSA) to the list of known hosts. [ 28.358132] random: sshd: uninitialized urandom read (32 bytes read, 120 bits of entropy available) executing program [ 28.455231] [ 28.456858] ====================================================== [ 28.463137] [ INFO: possible circular locking dependency detected ] [ 28.469507] 4.4.120-gd63fdf6 #28 Not tainted [ 28.473877] ------------------------------------------------------- [ 28.480244] syzkaller294477/3775 is trying to acquire lock: [ 28.485918] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 28.494493] [ 28.494493] but task is already holding lock: [ 28.500429] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 28.508917] [ 28.508917] which lock already depends on the new lock. [ 28.508917] [ 28.517198] [ 28.517198] the existing dependency chain (in reverse order) is: [ 28.524781] -> #1 (ashmem_mutex){+.+.+.}: [ 28.529525] [] lock_acquire+0x15e/0x460 [ 28.535766] [] mutex_lock_nested+0xbb/0x850 [ 28.542344] [] ashmem_mmap+0x53/0x400 [ 28.548395] [] mmap_region+0x94f/0x1250 [ 28.554618] [] do_mmap+0x4fd/0x9d0 [ 28.560409] [] vm_mmap_pgoff+0x16e/0x1c0 [ 28.566723] [] SyS_mmap_pgoff+0x33f/0x560 [ 28.573125] [] SyS_mmap+0x16/0x20 [ 28.578829] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 28.586011] -> #0 (&mm->mmap_sem){++++++}: [ 28.590849] [] __lock_acquire+0x371f/0x4b50 [ 28.597422] [] lock_acquire+0x15e/0x460 [ 28.603647] [] __might_fault+0x14a/0x1d0 [ 28.609961] [] ashmem_ioctl+0x3b4/0xfa0 [ 28.616181] [] do_vfs_ioctl+0x7aa/0xee0 [ 28.622406] [] SyS_ioctl+0x8f/0xc0 [ 28.628198] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 28.635377] [ 28.635377] other info that might help us debug this: [ 28.635377] [ 28.643482] Possible unsafe locking scenario: [ 28.643482] [ 28.649502] CPU0 CPU1 [ 28.654134] ---- ---- [ 28.658767] lock(ashmem_mutex); [ 28.662412] lock(&mm->mmap_sem); [ 28.668663] lock(ashmem_mutex); [ 28.674824] lock(&mm->mmap_sem); [ 28.678558] [ 28.678558] *** DEADLOCK *** [ 28.678558] [ 28.684581] 1 lock held by syzkaller294477/3775: [ 28.689299] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 28.698327] [ 28.698327] stack backtrace: [ 28.702787] CPU: 1 PID: 3775 Comm: syzkaller294477 Not tainted 4.4.120-gd63fdf6 #28 [ 28.710546] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.719864] 0000000000000000 3ad5b4ce52500e73 ffff8801c575f9b8 ffffffff81d0408d [ 28.727819] ffffffff851a0010 ffffffff851a0010 ffffffff851bdf50 ffff8801d97a68f8 [ 28.735780] ffff8801d97a6000 ffff8801c575fa00 ffffffff81233ba1 ffff8801d97a68f8 [ 28.743735] Call Trace: [ 28.746288] [] dump_stack+0xc1/0x124 [ 28.751617] [] print_circular_bug+0x271/0x310 [ 28.757728] [] __lock_acquire+0x371f/0x4b50 [ 28.763670] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 28.770650] [] ? mark_held_locks+0xaf/0x100 [ 28.776585] [] ? __lock_is_held+0xa1/0xf0 [ 28.782348] [] lock_acquire+0x15e/0x460 [ 28.787939] [] ? __might_fault+0xe4/0x1d0 [ 28.793700] [] __might_fault+0x14a/0x1d0 [ 28.799377] [] ? __might_fault+0xe4/0x1d0 [ 28.805139] [] ashmem_ioctl+0x3b4/0xfa0 [ 28.810730] [] ? mmap_region+0x3f9/0x1250 [ 28.816493] [] ? ashmem_shrink_scan+0x390/0x390 [ 28.822776] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 28.828625] [] ? ashmem_shrink_scan+0x390/0x390 [ 28.834907] [] do_vfs_ioctl+0x7aa/0xee0 [ 28.840496] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 28.846693] [] ? fput+0x20/0x150 [ 28.851676] [] ? SyS_mmap_pgoff+0xd8/0x