compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
{
	int i;
	int num_subauth, num_sat, num_saw;

	if ((!ctsid) || (!cwsid))
		return 1;

	/* compare the revision */
	if (ctsid->revision != cwsid->revision) {
		if (ctsid->revision > cwsid->revision)
			return 1;
		else
			return -1;
	}

	/* compare all of the six auth values */
	for (i = 0; i < NUM_AUTHS; ++i) {
		if (ctsid->authority[i] != cwsid->authority[i]) {
			if (ctsid->authority[i] > cwsid->authority[i])
				return 1;
			else
				return -1;
		}
	}

	/* compare all of the subauth values if any */
	num_sat = ctsid->num_subauth;
	num_saw = cwsid->num_subauth;
	num_subauth = num_sat < num_saw ? num_sat : num_saw;
	if (num_subauth) {
		for (i = 0; i < num_subauth; ++i) {
			if (ctsid->sub_auth[i] != cwsid->sub_auth[i]) {
				if (le32_to_cpu(ctsid->sub_auth[i]) >
					le32_to_cpu(cwsid->sub_auth[i]))
					return 1;
				else
					return -1;
			}
		}
	}

	return 0; /* sids compare/match */
}

The product dereferences a pointer that it expects to be valid but is NULL.