xfrm: make aead_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

@@ -1764,7 +1764,7 @@ static inline int xfrm_acquire_is_on(struct net *net)
 }
 #endif
 
-static inline int aead_len(struct xfrm_algo_aead *alg)
+static inline unsigned int aead_len(struct xfrm_algo_aead *alg)
 {
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
 }

net/xfrm/xfrm_user.c

@@ -84,7 +84,7 @@ static int verify_aead(struct nlattr **attrs)
 		return 0;
 
 	algp = nla_data(rt);
-	if (nla_len(rt) < aead_len(algp))
+	if (nla_len(rt) < (int)aead_len(algp))
 		return -EINVAL;
 
 	algp->alg_name[sizeof(algp->alg_name) - 1] = '\0';