[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.855334] 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: [ 25.301259] random: sshd: uninitialized urandom read (32 bytes read, 38 bits of entropy available) [ 25.801382] random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available) [ 26.817884] random: sshd: uninitialized urandom read (32 bytes read, 109 bits of entropy available) [ 27.001722] random: sshd: uninitialized urandom read (32 bytes read, 115 bits of entropy available) Warning: Permanently added '10.128.0.18' (ECDSA) to the list of known hosts. [ 32.452293] random: sshd: uninitialized urandom read (32 bytes read, 122 bits of entropy available) executing program [ 32.550204] [ 32.551836] ====================================================== [ 32.558129] [ INFO: possible circular locking dependency detected ] [ 32.564501] 4.4.120-gd63fdf6 #28 Not tainted [ 32.568875] ------------------------------------------------------- [ 32.575248] syzkaller266176/3785 is trying to acquire lock: [ 32.580924] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 32.589505] [ 32.589505] but task is already holding lock: [ 32.595447] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 32.603940] [ 32.603940] which lock already depends on the new lock. [ 32.603940] [ 32.612226] [ 32.612226] the existing dependency chain (in reverse order) is: [ 32.619813] -> #1 (ashmem_mutex){+.+.+.}: [ 32.624591] [] lock_acquire+0x15e/0x460 [ 32.630824] [] mutex_lock_nested+0xbb/0x850 [ 32.637404] [] ashmem_mmap+0x53/0x400 [ 32.643461] [] mmap_region+0x94f/0x1250 [ 32.649700] [] do_mmap+0x4fd/0x9d0 [ 32.655492] [] vm_mmap_pgoff+0x16e/0x1c0 [ 32.661815] [] SyS_mmap_pgoff+0x33f/0x560 [ 32.668229] [] SyS_mmap+0x16/0x20 [ 32.674007] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 32.681236] -> #0 (&mm->mmap_sem){++++++}: [ 32.686076] [] __lock_acquire+0x371f/0x4b50 [ 32.692662] [] lock_acquire+0x15e/0x460 [ 32.698897] [] __might_fault+0x14a/0x1d0 [ 32.705222] [] ashmem_ioctl+0x3b4/0xfa0 [ 32.711459] [] do_vfs_ioctl+0x7aa/0xee0 [ 32.717696] [] SyS_ioctl+0x8f/0xc0 [ 32.723486] [] entry_SYSCALL_64_fastpath+0x1c/0x98 [ 32.730674] [ 32.730674] other info that might help us debug this: [ 32.730674] [ 32.738787] Possible unsafe locking scenario: [ 32.738787] [ 32.744810] CPU0 CPU1 [ 32.749442] ---- ---- [ 32.754077] lock(ashmem_mutex); [ 32.757732] lock(&mm->mmap_sem); [ 32.763988] lock(ashmem_mutex); [ 32.770154] lock(&mm->mmap_sem); [ 32.773891] [ 32.773891] *** DEADLOCK *** [ 32.773891] [ 32.780700] 1 lock held by syzkaller266176/3785: [ 32.785429] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x367/0xfa0 [ 32.794472] [ 32.794472] stack backtrace: [ 32.798938] CPU: 1 PID: 3785 Comm: syzkaller266176 Not tainted 4.4.120-gd63fdf6 #28 [ 32.806696] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.816025] 0000000000000000 8a770c4c25e4ba0f ffff8800bb2179b8 ffffffff81d0408d [ 32.823987] ffffffff851a0010 ffffffff851a0010 ffffffff851be100 ffff8800abf608f8 [ 32.832039] ffff8800abf60000 ffff8800bb217a00 ffffffff81233ba1 ffff8800abf608f8 [ 32.839998] Call Trace: [ 32.842559] [] dump_stack+0xc1/0x124 [ 32.847889] [] print_circular_bug+0x271/0x310 [ 32.854008] [] __lock_acquire+0x371f/0x4b50 [ 32.859949] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 32.866926] [] ? mark_held_locks+0xaf/0x100 [ 32.872862] [] ? __lock_is_held+0xa1/0xf0 [ 32.878627] [] lock_acquire+0x15e/0x460 [ 32.884219] [] ? __might_fault+0xe4/0x1d0 [ 32.889990] [] __might_fault+0x14a/0x1d0 [ 32.895665] [] ? __might_fault+0xe4/0x1d0 [ 32.901437] [] ashmem_ioctl+0x3b4/0xfa0 [ 32.907034] [] ? mmap_region+0x3f9/0x1250 [ 32.912796] [] ? ashmem_shrink_scan+0x390/0x390 [ 32.919084] [] ? vm_mmap_pgoff+0x180/0x1c0 [ 32.924935] [] ? ashmem_shrink_scan+0x390/0x390 [ 32.931227] [] do_vfs_ioctl+0x7aa/0xee0 [ 32.936831] [] ? ioctl_preallocate+0x1f0/0x1f0 [ 32.943037] [] ? fput+0x20/0x150 [ 32.948021] [] ? SyS_mmap