On Fri, Aug 18, 2017 at 03:15:18PM -0600, Liu Bo wrote:

An invalid value of extent inline ref type may be read from a
malicious image which may force btrfs to crash.

This adds a helper which does sanity check for the ref type, so we can
know if it's sane, return type if so, otherwise return an error.

Signed-off-by: Liu Bo <redacted>

Reviewed-by: David Sterba <dsterba@suse.com>