xfrm: make xfrm_alg_len() return unsigned int

Key lengths can't be negative.

Comparison with nla_len() is left signed just in case negative value
can sneak in there.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -1769,7 +1769,7 @@ static inline unsigned int aead_len(struct xfrm_algo_aead *alg)
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
 }
 
-static inline int xfrm_alg_len(const struct xfrm_algo *alg)
+static inline unsigned int xfrm_alg_len(const struct xfrm_algo *alg)
 {
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
 }

net/xfrm/xfrm_user.c

@@ -42,7 +42,7 @@ static int verify_one_alg(struct nlattr **attrs, enum xfrm_attr_type_t type)
 		return 0;
 
 	algp = nla_data(rt);
-	if (nla_len(rt) < xfrm_alg_len(algp))
+	if (nla_len(rt) < (int)xfrm_alg_len(algp))
 		return -EINVAL;
 
 	switch (type) {