[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.053489] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 25.012456] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 25.490061] random: sshd: uninitialized urandom read (32 bytes read, 39 bits of entropy available) [ 26.240712] random: sshd: uninitialized urandom read (32 bytes read, 69 bits of entropy available) [ 26.421957] random: sshd: uninitialized urandom read (32 bytes read, 73 bits of entropy available) Warning: Permanently added '10.128.0.9' (ECDSA) to the list of known hosts. [ 31.825160] random: sshd: uninitialized urandom read (32 bytes read, 81 bits of entropy available) executing program [ 31.923656] [ 31.925293] ====================================================== [ 31.931581] [ INFO: possible circular locking dependency detected ] [ 31.937955] 4.4.120-gd63fdf6 #28 Not tainted [ 31.942327] ------------------------------------------------------- [ 31.948695] syzkaller314224/3717 is trying to acquire lock: [ 31.954367] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 31.962955] [ 31.962955] but task is already holding lock: [ 31.968898] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 31.977380] [ 31.977380] which lock already depends on the new lock. [ 31.977380] [ 31.985660] [ 31.985660] the existing dependency chain (in reverse order) is: [ 31.993246] -> #1 (ashmem_mutex){+.+.+.}: [ 31.998002] [] lock_acquire+0x15e/0x460 [ 32.004228] [] mutex_lock_nested+0xbb/0x850 [ 32.010803] [] ashmem_mmap+0x53/0x400 [ 32.016857] [] mmap_region+0x94f/0x1250 [ 32.023092] [] do_mmap+0x4fd/0x9d0 [ 32.028886] [] vm_mmap_pgoff+0x16e/0x1c0 [ 32.035201] [] SyS_mmap_pgoff+0x33f/0x560 [ 32.041602] [] SyS_mmap+0x16/0x20 [ 32.047309] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 32.054491] -> #0 (&mm->mmap_sem){++++++}: [ 32.059328] [] __lock_acquire+0x371f/0x4b50 [ 32.065899] [] lock_acquire+0x15e/0x460 [ 32.072131] [] __might_fault+0x14a/0x1d0 [ 32.078445] [] ashmem_ioctl+0x3b4/0xfa0 [ 32.084671] [] do_vfs_ioctl+0x7aa/0xee0 [ 32.090901] [] SyS_ioctl+0x8f/0xc0 [ 32.096709] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 32.103891] [ 32.103891] other info that might help us debug this: [ 32.103891] [ 32.112005] Possible unsafe locking scenario: [ 32.112005] [ 32.118028] CPU0 CPU1 [ 32.122660] ---- ---- [ 32.127291] lock(ashmem_mutex); [ 32.130939] lock(&mm->mmap_sem); [ 32.137200] lock(ashmem_mutex); [ 32.143370] lock(&mm->mmap_sem); [ 32.147104] [ 32.147104] *** DEADLOCK *** [ 32.147104] [ 32.153139] 1 lock held by syzkaller314224/3717: [ 32.157858] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 32.166896] [ 32.166896] stack backtrace: [ 32.171362] CPU: 0 PID: 3717 Comm: syzkaller314224 Not tainted 4.4.120-gd63fdf6 #28 [ 32.179120] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.188438] 0000000000000000 19d10a545b88d48c ffff8801cf3079b8 ffffffff81d0408d [ 32.196400] ffffffff8519fe60 ffffffff8519fe60 ffffffff851bdda0 ffff8800adfa20f8 [ 32.204364] ffff8800adfa1800 ffff8801cf307a00 ffffffff81233ba1 ffff8800adfa20f8 [ 32.212325] Call Trace: [ 32.214878] [] dump_stack+0xc1/0x124 [ 32.220209] [] print_circular_bug+0x271/0x310 [ 32.226322] [] __lock_acquire+0x371f/0x4b50 [ 32.232260] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 32.239236] [] ? mark_held_locks+0xaf/0x100 [ 32.245172] [] ? __lock_is_held+0xa1/0xf0 [ 32.250939] [] lock_acquire+0x15e/0x460 [ 32.256528] [] ? __might_fault+0xe4/0x1d0 [ 32.262290] [] __might_fault+0x14a/0x1d0 [ 32.267970] [] ? __might_fault+0xe4/0x1d0 [ 32.273735] [] ashmem_ioctl+0x3b4/0xfa0 [ 32.279323] [] ? mmap_region+0x3f9/0x1250 [ 32.285086] [] ? ashmem_shrink_scan+0x390/0x390 [ 32.291370] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 32.297220] [] ? ashmem_shrink_scan+0x390/0x390 [ 32.303507] [] do_vfs_ioctl+0x7aa/0xee0 [ 32.309097] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 32.315294] [] ? fput+0x20/0x150 [ 32.320276] [] ? SyS_mmap_pgoff+0xd8/0