[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 22.029770] random: sshd: uninitialized urandom read (32 bytes read, 34 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 25.719430] random: sshd: uninitialized urandom read (32 bytes read, 38 bits of entropy available) [ 26.201211] random: sshd: uninitialized urandom read (32 bytes read, 38 bits of entropy available) [ 27.162925] random: sshd: uninitialized urandom read (32 bytes read, 118 bits of entropy available) [ 27.346792] random: sshd: uninitialized urandom read (32 bytes read, 124 bits of entropy available) [ 31.478160] random: nonblocking pool is initialized Warning: Permanently added '10.128.15.207' (ECDSA) to the list of known hosts. executing program [ 32.832783] [ 32.834447] ====================================================== [ 32.840732] [ INFO: possible circular locking dependency detected ] [ 32.847130] 4.4.118-g5f7f76a #24 Not tainted [ 32.851504] ------------------------------------------------------- [ 32.857876] syzkaller058820/3796 is trying to acquire lock: [ 32.863557] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 32.872152] [ 32.872152] but task is already holding lock: [ 32.878093] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 32.886604] [ 32.886604] which lock already depends on the new lock. [ 32.886604] [ 32.894886] [ 32.894886] the existing dependency chain (in reverse order) is: [ 32.902475] -> #1 (ashmem_mutex){+.+.+.}: [ 32.907238] [] lock_acquire+0x15e/0x460 [ 32.913474] [] mutex_lock_nested+0xbb/0x850 [ 32.920055] [] ashmem_mmap+0x53/0x400 [ 32.926109] [] mmap_region+0x94f/0x1250 [ 32.932341] [] do_mmap+0x4fd/0x9d0 [ 32.938134] [] vm_mmap_pgoff+0x16e/0x1c0 [ 32.944452] [] SyS_mmap_pgoff+0x33f/0x560 [ 32.950859] [] SyS_mmap+0x16/0x20 [ 32.956577] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 32.963762] -> #0 (&mm->mmap_sem){++++++}: [ 32.968610] [] __lock_acquire+0x371f/0x4b50 [ 32.975200] [] lock_acquire+0x15e/0x460 [ 32.981435] [] __might_fault+0x14a/0x1d0 [ 32.987753] [] ashmem_ioctl+0x3b4/0xfa0 [ 32.993982] [] do_vfs_ioctl+0x7aa/0xee0 [ 33.000230] [] SyS_ioctl+0x8f/0xc0 [ 33.006038] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 33.013234] [ 33.013234] other info that might help us debug this: [ 33.013234] [ 33.021357] Possible unsafe locking scenario: [ 33.021357] [ 33.027382] CPU0 CPU1 [ 33.032019] ---- ---- [ 33.036652] lock(ashmem_mutex); [ 33.040301] lock(&mm->mmap_sem); [ 33.046552] lock(ashmem_mutex); [ 33.052732] lock(&mm->mmap_sem); [ 33.056475] [ 33.056475] *** DEADLOCK *** [ 33.056475] [ 33.062508] 1 lock held by syzkaller058820/3796: [ 33.067230] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 33.076281] [ 33.076281] stack backtrace: [ 33.080758] CPU: 1 PID: 3796 Comm: syzkaller058820 Not tainted 4.4.118-g5f7f76a #24 [ 33.088523] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.097848] 0000000000000000 8175c68a41d66ed2 ffff8800b76879b8 ffffffff81d0402d [ 33.105825] ffffffff851a0010 ffffffff851a0010 ffffffff851be610 ffff8801c53d38f8 [ 33.113812] ffff8801c53d3000 ffff8800b7687a00 ffffffff81233ba1 ffff8801c53d38f8 [ 33.121776] Call Trace: [ 33.124341] [] dump_stack+0xc1/0x124 [ 33.129674] [] print_circular_bug+0x271/0x310 [ 33.135833] [] __lock_acquire+0x371f/0x4b50 [ 33.141776] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 33.148761] [] ? mark_held_locks+0xaf/0x100 [ 33.154703] [] ? __lock_is_held+0xa1/0xf0 [ 33.160469] [] lock_acquire+0x15e/0x460 [ 33.166069] [] ? __might_fault+0xe4/0x1d0 [ 33.171873] [] __might_fault+0x14a/0x1d0 [ 33.177554] [] ? __might_fault+0xe4/0x1d0 [ 33.183329] [] ashmem_ioctl+0x3b4/0xfa0 [ 33.188922] [] ? mmap_region+0x3f9/0x1250 [ 33.194690] [] ? ashmem_shrink_scan+0x390/0x390 [ 33.200982] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 33.206937] [] ? ashmem_shrink_scan+0x390/0x390 [ 33.213231] [] do_vfs_ioctl+0x7aa/0xee0 [ 33.218835] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 33.225148] [] ? fput+0x20/0x150 [ 33.230136] [] ? SyS_mmap_pg