random: sshd: uninitialized urandom read (32 bytes read, 117 bits of entropy available)

======================================================
[ INFO: possible circular locking dependency detected ]
4.4.112-gca0ebb4 #22 Not tainted
-------------------------------------------------------
syzkaller008408/3323 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff814627a1>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816

but task is already holding lock:
 (ashmem_mutex){+.+.+.}, at: [<ffffffff82c64806>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff8123c7be>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff8376ce7b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8376ce7b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
       [<ffffffff82c63c53>] ashmem_mmap+0x53/0x400 drivers/staging/android/ashmem.c:366
       [<ffffffff814b047f>] mmap_region+0x94f/0x1250 mm/mmap.c:1664
       [<ffffffff814b127d>] do_mmap+0x4fd/0x9d0 mm/mmap.c:1441
       [<ffffffff8146f4be>] do_mmap_pgoff include/linux/mm.h:1915 [inline]
       [<ffffffff8146f4be>] vm_mmap_pgoff+0x16e/0x1c0 mm/util.c:272
       [<ffffffff814af44f>] SYSC_mmap_pgoff mm/mmap.c:1491 [inline]
       [<ffffffff814af44f>] SyS_mmap_pgoff+0x33f/0x560 mm/mmap.c:1449
       [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
       [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
       [<ffffffff83777d6a>] sysenter_flags_fixed+0xd/0x17

       [<ffffffff8123c7be>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff81494c4a>] __might_fault+0x14a/0x1d0 mm/memory.c:3810
       [<ffffffff8155a742>] copy_to_user arch/x86/include/asm/uaccess.h:760 [inline]
       [<ffffffff8155a742>] filldir+0x162/0x2d0 fs/readdir.c:180
       [<ffffffff81597ece>] dir_emit_dot include/linux/fs.h:3070 [inline]
       [<ffffffff81597ece>] dir_emit_dots include/linux/fs.h:3081 [inline]
       [<ffffffff81597ece>] dcache_readdir+0x11e/0x7b0 fs/libfs.c:150
       [<ffffffff8155a388>] iterate_dir+0x1c8/0x420 fs/readdir.c:42
       [<ffffffff8155b07a>] SYSC_getdents fs/readdir.c:215 [inline]
       [<ffffffff8155b07a>] SyS_getdents+0x14a/0x270 fs/readdir.c:196
       [<ffffffff837763d9>] entry_SYSCALL_64_fastpath+0x16/0x92

       [<ffffffff81239b1f>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81239b1f>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81239b1f>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81239b1f>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
       [<ffffffff8123c7be>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff8376ce7b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8376ce7b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
       [<ffffffff814627a1>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
       [<ffffffff8151c0d2>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
       [<ffffffff82c64897>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
       [<ffffffff8151e04b>] vfs_llseek fs/read_write.c:260 [inline]
       [<ffffffff8151e04b>] SYSC_lseek fs/read_write.c:285 [inline]
       [<ffffffff8151e04b>] SyS_lseek fs/read_write.c:276 [inline]
       [<ffffffff8151e04b>] C_SYSC_lseek fs/read_write.c:297 [inline]
       [<ffffffff8151e04b>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
       [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
       [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
       [<ffffffff83777d6a>] sysenter_flags_fixed+0xd/0x17

other info that might help us debug this:

Chain exists of:
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(ashmem_mutex);
                               lock(&mm->mmap_sem);
                               lock(ashmem_mutex);
  lock(&sb->s_type->i_mutex_key#10);

 *** DEADLOCK ***

1 lock held by syzkaller008408/3323:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82c64806>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

stack backtrace:
CPU: 1 PID: 3323 Comm: syzkaller008408 Not tainted 4.4.112-gca0ebb4 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 58661873ae2e734c ffff8800b44b7a58 ffffffff81d056fd
 ffffffff8519e880 ffffffff851a7eb0 ffffffff851bc460 ffff8800b5df2058
 ffff8800b5df17c0 ffff8800b44b7aa0 ffffffff81232b91 ffff8800b5df2058
Call Trace:
 [<ffffffff81d056fd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d056fd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81232b91>] print_circular_bug+0x271/0x310 kernel/locking/lockdep.c:1226
 [<ffffffff81239b1f>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81239b1f>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81239b1f>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81239b1f>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
 [<ffffffff8123c7be>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
 [<ffffffff8376ce7b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff8376ce7b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
 [<ffffffff814627a1>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
 [<ffffffff8151c0d2>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
 [<ffffffff82c64897>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
 [<ffffffff8151e04b>] vfs_llseek fs/read_write.c:260 [inline]
 [<ffffffff8151e04b>] SYSC_lseek fs/read_write.c:285 [inline]
 [<ffffffff8151e04b>] SyS_lseek fs/read_write.c:276 [inline]
 [<ffffffff8151e04b>] C_SYSC_lseek fs/read_write.c:297 [inline]
 [<ffffffff8151e04b>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
 [<ffffffff81006d84>] do_fast_syscall_