The directory may have been removed when entering
fscrypt_ioctl_set_policy(). If so, the empty_dir() check will return
error for ext4 file system.
ext4_rmdir() sets i_size = 0, then ext4_empty_dir() reports an error
because 'inode->i_size < EXT4_DIR_REC_LEN(1) + EXT4_DIR_REC_LEN(2)'. If
the fs is mounted with errors=panic, it will trigger a panic issue.
Add the check IS_DEADDIR() to fix this problem.
Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support") Cc: <stable@vger.kernel.org> # v4.1+ Signed-off-by: Hongjie Fang <hongjiefang@asrmicro.com> Signed-off-by: Eric Biggers <ebiggers@google.com>