[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.228089] 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 [ 20.411408] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) syzkaller login: [ 20.748221] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 21.683702] random: sshd: uninitialized urandom read (32 bytes read, 105 bits of entropy available) [ 21.854380] random: sshd: uninitialized urandom read (32 bytes read, 109 bits of entropy available) Warning: Permanently added '10.128.0.36' (ECDSA) to the list of known hosts. [ 27.268915] random: sshd: uninitialized urandom read (32 bytes read, 118 bits of entropy available) executing program [ 27.366018] [ 27.367663] ====================================================== [ 27.373951] [ INFO: possible circular locking dependency detected ] [ 27.380321] 4.4.120-gd63fdf6 #28 Not tainted [ 27.384691] ------------------------------------------------------- [ 27.391059] syzkaller812725/3645 is trying to acquire lock: [ 27.396731] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.405303] [ 27.405303] but task is already holding lock: [ 27.411237] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 27.419718] [ 27.419718] which lock already depends on the new lock. [ 27.419718] [ 27.427999] [ 27.427999] the existing dependency chain (in reverse order) is: [ 27.435582] -> #1 (ashmem_mutex){+.+.+.}: [ 27.440324] [] lock_acquire+0x15e/0x460 [ 27.446548] [] mutex_lock_nested+0xbb/0x850 [ 27.453124] [] ashmem_mmap+0x53/0x400 [ 27.459175] [] mmap_region+0x94f/0x1250 [ 27.465402] [] do_mmap+0x4fd/0x9d0 [ 27.471193] [] vm_mmap_pgoff+0x16e/0x1c0 [ 27.477512] [] SyS_mmap_pgoff+0x33f/0x560 [ 27.483918] [] SyS_mmap+0x16/0x20 [ 27.489621] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 27.496803] -> #0 (&mm->mmap_sem){++++++}: [ 27.501631] [] __lock_acquire+0x371f/0x4b50 [ 27.508203] [] lock_acquire+0x15e/0x460 [ 27.514444] [] __might_fault+0x14a/0x1d0 [ 27.520754] [] ashmem_ioctl+0x3b4/0xfa0 [ 27.526980] [] do_vfs_ioctl+0x7aa/0xee0 [ 27.533204] [] SyS_ioctl+0x8f/0xc0 [ 27.538997] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 27.546181] [ 27.546181] other info that might help us debug this: [ 27.546181] [ 27.554287] Possible unsafe locking scenario: [ 27.554287] [ 27.560310] CPU0 CPU1 [ 27.564943] ---- ---- [ 27.569575] lock(ashmem_mutex); [ 27.573222] lock(&mm->mmap_sem); [ 27.579472] lock(ashmem_mutex); [ 27.585630] lock(&mm->mmap_sem); [ 27.589364] [ 27.589364] *** DEADLOCK *** [ 27.589364] [ 27.595391] 1 lock held by syzkaller812725/3645: [ 27.600108] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 27.609146] [ 27.609146] stack backtrace: [ 27.613608] CPU: 1 PID: 3645 Comm: syzkaller812725 Not tainted 4.4.120-gd63fdf6 #28 [ 27.621368] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.630688] 0000000000000000 2b6e861fe21cd542 ffff8800af03f9b8 ffffffff81d0408d [ 27.638644] ffffffff8519fe60 ffffffff8519fe60 ffffffff851bdbf0 ffff8801ccc068f8 [ 27.646602] ffff8801ccc06000 ffff8800af03fa00 ffffffff81233ba1 ffff8801ccc068f8 [ 27.654563] Call Trace: [ 27.657122] [] dump_stack+0xc1/0x124 [ 27.662459] [] print_circular_bug+0x271/0x310 [ 27.668571] [] __lock_acquire+0x371f/0x4b50 [ 27.674508] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.681487] [] ? mark_held_locks+0xaf/0x100 [ 27.687428] [] ? __lock_is_held+0xa1/0xf0 [ 27.693197] [] lock_acquire+0x15e/0x460 [ 27.698788] [] ? __might_fault+0xe4/0x1d0 [ 27.704563] [] __might_fault+0x14a/0x1d0 [ 27.710240] [] ? __might_fault+0xe4/0x1d0 [ 27.716002] [] ashmem_ioctl+0x3b4/0xfa0 [ 27.721597] [] ? mmap_region+0x3f9/0x1250 [ 27.727363] [] ? ashmem_shrink_scan+0x390/0x390 [ 27.733657] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 27.739510] [] ? ashmem_shrink_scan+0x390/0x390 [ 27.745797] [] do_vfs_ioctl+0x7aa/0xee0 [ 27.751388] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 27.757585] [] ? fput+0x20/0x150 [ 27.762578] [] ? SyS_mmap_pgoff+0xd8/0x5