urandom_read: 1 callbacks suppressed
random: sshd: uninitialized urandom read (32 bytes read)

======================================================
[ INFO: possible circular locking dependency detected ]
4.9.119-g9dc978d #23 Not tainted
-------------------------------------------------------
syz-executor052/3784 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#10){++++++}, at: [<ffffffff81493d3c>] inode_lock include/linux/fs.h:766 [inline]
 (&sb->s_type->i_mutex_key#10){++++++}, at: [<ffffffff81493d3c>] shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
but task is already holding lock:
 (ashmem_mutex){+.+.+.}, at: [<ffffffff82e41085>] ashmem_shrink_scan+0x55/0x3a0 drivers/staging/android/ashmem.c:449
which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
       __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621
       ashmem_mmap+0x53/0x3f0 drivers/staging/android/ashmem.c:378
       mmap_region+0x893/0x1040 mm/mmap.c:1726
       do_mmap+0x59c/0xcc0 mm/mmap.c:1505
       do_mmap_pgoff include/linux/mm.h:2032 [inline]
       vm_mmap_pgoff+0x168/0x1b0 mm/util.c:329
       SYSC_mmap_pgoff mm/mmap.c:1555 [inline]
       SyS_mmap_pgoff+0x342/0x550 mm/mmap.c:1513
       SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline]
       SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87
       do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
       entry_SYSCALL_64_after_swapgs+0x5d/0xdb

       lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
       __might_fault+0x14a/0x1d0 mm/memory.c:4014
       copy_to_user arch/x86/include/asm/uaccess.h:727 [inline]
       filldir+0x1a4/0x370 fs/readdir.c:195
       dir_emit_dot include/linux/fs.h:3241 [inline]
       dir_emit_dots include/linux/fs.h:3252 [inline]
       dcache_readdir+0x130/0x5d0 fs/libfs.c:191
       iterate_dir+0x1ac/0x600 fs/readdir.c:50
       SYSC_getdents fs/readdir.c:230 [inline]
       SyS_getdents+0x13c/0x2a0 fs/readdir.c:211
       do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
       entry_SYSCALL_64_after_swapgs+0x5d/0xdb

       check_prev_add kernel/locking/lockdep.c:1828 [inline]
       check_prevs_add kernel/locking/lockdep.c:1938 [inline]
       validate_chain kernel/locking/lockdep.c:2265 [inline]
       __lock_acquire+0x3019/0x4070 kernel/locking/lockdep.c:3345
       lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
       down_write+0x41/0xa0 kernel/locking/rwsem.c:52
       inode_lock include/linux/fs.h:766 [inline]
       shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
       ashmem_shrink_scan+0x1bd/0x3a0 drivers/staging/android/ashmem.c:456
       ashmem_ioctl+0x2c1/0xf20 drivers/staging/android/ashmem.c:798
       vfs_ioctl fs/ioctl.c:43 [inline]
       file_ioctl fs/ioctl.c:493 [inline]
       do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
       SYSC_ioctl fs/ioctl.c:694 [inline]
       SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
       do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
       entry_SYSCALL_64_after_swapgs+0x5d/0xdb

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 syz-executor052/3784:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82e41085>] ashmem_shrink_scan+0x55/0x3a0 drivers/staging/android/ashmem.c:449

stack backtrace:
CPU: 0 PID: 3784 Comm: syz-executor052 Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801ba607638 ffffffff81eb4be9 ffffffff855d09d0 ffffffff855eeac0
 ffffffff855d7e40 ffff8801bb19d0e8 ffff8801bb19c800 ffff8801ba607680
 ffffffff81426644 0000000000000001 00000000bb19c800 0000000000000001
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81426644>] print_circular_bug.cold.51+0x1bd/0x27d kernel/locking/lockdep.c:1202
 [<ffffffff812391a9>] check_prev_add kernel/locking/lockdep.c:1828 [inline]
 [<ffffffff812391a9>] check_prevs_add kernel/locking/lockdep.c:1938 [inline]
 [<ffffffff812391a9>] validate_chain kernel/locking/lockdep.c:2265 [inline]
 [<ffffffff812391a9>] __lock_acquire+0x3019/0x4070 kernel/locking/lockdep.c:3345
 [<ffffffff8123ac70>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff839f67c1>] down_write+0x41/0xa0 kernel/locking/rwsem.c:52
 [<ffffffff81493d3c>] inode_lock include/linux/fs.h:766 [inline]
 [<ffffffff81493d3c>] shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
 [<ffffffff82e411ed>] ashmem_shrink_scan+0x1bd/0x3a0 drivers/staging/android/ashmem.c:456
 [<ffffffff82e418c1>] ashmem_ioctl+0x2c1/0xf20 drivers/staging/android/ashmem.c:798
 [<ffffffff815b309c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b309c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b309c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b411f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b411f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/