[ 19.717641] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [ 20.167761] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [ 20.499311] random: sshd: uninitialized urandom read (32 bytes read, 34 bits of entropy available) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.385985] random: sshd: uninitialized urandom read (32 bytes read, 102 bits of entropy available) [ 21.981092] random: sshd: uninitialized urandom read (32 bytes read, 106 bits of entropy available) Warning: Permanently added '10.128.0.44' (ECDSA) to the list of known hosts. [ 27.397806] random: sshd: uninitialized urandom read (32 bytes read, 113 bits of entropy available) executing program [ 27.495331] [ 27.496971] ====================================================== [ 27.503255] [ INFO: possible circular locking dependency detected ] [ 27.509627] 4.4.120-gd63fdf6 #28 Not tainted [ 27.514113] ------------------------------------------------------- [ 27.520484] syzkaller586901/3625 is trying to acquire lock: [ 27.526174] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.534747] [ 27.534747] but task is already holding lock: [ 27.540685] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 27.549181] [ 27.549181] which lock already depends on the new lock. [ 27.549181] [ 27.557467] [ 27.557467] the existing dependency chain (in reverse order) is: [ 27.565068] -> #1 (ashmem_mutex){+.+.+.}: [ 27.569815] [] lock_acquire+0x15e/0x460 [ 27.576054] [] mutex_lock_nested+0xbb/0x850 [ 27.582637] [] ashmem_mmap+0x53/0x400 [ 27.588693] [] mmap_region+0x94f/0x1250 [ 27.594920] [] do_mmap+0x4fd/0x9d0 [ 27.600714] [] vm_mmap_pgoff+0x16e/0x1c0 [ 27.607045] [] SyS_mmap_pgoff+0x33f/0x560 [ 27.613450] [] SyS_mmap+0x16/0x20 [ 27.619170] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 27.626363] -> #0 (&mm->mmap_sem){++++++}: [ 27.631201] [] __lock_acquire+0x371f/0x4b50 [ 27.637776] [] lock_acquire+0x15e/0x460 [ 27.644000] [] __might_fault+0x14a/0x1d0 [ 27.650314] [] ashmem_ioctl+0x3b4/0xfa0 [ 27.656541] [] do_vfs_ioctl+0x7aa/0xee0 [ 27.662770] [] SyS_ioctl+0x8f/0xc0 [ 27.668573] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 27.675768] [ 27.675768] other info that might help us debug this: [ 27.675768] [ 27.683878] Possible unsafe locking scenario: [ 27.683878] [ 27.689902] CPU0 CPU1 [ 27.694536] ---- ---- [ 27.699168] lock(ashmem_mutex); [ 27.702819] lock(&mm->mmap_sem); [ 27.709075] lock(ashmem_mutex); [ 27.715235] lock(&mm->mmap_sem); [ 27.718967] [ 27.718967] *** DEADLOCK *** [ 27.718967] [ 27.724995] 1 lock held by syzkaller586901/3625: [ 27.729716] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 27.738761] [ 27.738761] stack backtrace: [ 27.743316] CPU: 0 PID: 3625 Comm: syzkaller586901 Not tainted 4.4.120-gd63fdf6 #28 [ 27.751085] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.760409] 0000000000000000 4e7d9aa2dbd62a72 ffff8801cc8bf9b8 ffffffff81d0408d [ 27.768370] ffffffff851a0010 ffffffff851a0010 ffffffff851bdf50 ffff8801ce9a88f8 [ 27.776342] ffff8801ce9a8000 ffff8801cc8bfa00 ffffffff81233ba1 ffff8801ce9a88f8 [ 27.784302] Call Trace: [ 27.786861] [] dump_stack+0xc1/0x124 [ 27.792194] [] print_circular_bug+0x271/0x310 [ 27.798305] [] __lock_acquire+0x371f/0x4b50 [ 27.804244] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.811239] [] ? mark_held_locks+0xaf/0x100 [ 27.817189] [] ? __lock_is_held+0xa1/0xf0 [ 27.822957] [] lock_acquire+0x15e/0x460 [ 27.828550] [] ? __might_fault+0xe4/0x1d0 [ 27.834314] [] __might_fault+0x14a/0x1d0 [ 27.839994] [] ? __might_fault+0xe4/0x1d0 [ 27.845758] [] ashmem_ioctl+0x3b4/0xfa0 [ 27.851347] [] ? mmap_region+0x3f9/0x1250 [ 27.857118] [] ? ashmem_shrink_scan+0x390/0x390 [ 27.863403] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 27.869255] [] ? ashmem_shrink_scan+0x390/0x390 [ 27.875541] [] do_vfs_ioctl+0x7aa/0xee0 [ 27.881131] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 27.887332] [] ? fput+0x20/0x150 [ 27.892317] [] ? SyS_mmap_pgoff+0