xfrm: check trunc_len in XFRMA_ALG_AUTH_TRUNC

Maximum trunc length is defined by MAX_AH_AUTH_LEN (in bytes)
and need to be checked when this value is set (in bits) by
the user. In ah4.c and ah6.c a BUG_ON() checks this condiftion.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_user.c

@@ -26,6 +26,7 @@
 #include <net/sock.h>
 #include <net/xfrm.h>
 #include <net/netlink.h>
+#include <net/ah.h>
 #include <asm/uaccess.h>
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 #include <linux/in6.h>
@@ -302,7 +303,8 @@ static int attach_auth_trunc(struct xfrm_algo_auth **algpp, u8 *props,
 	algo = xfrm_aalg_get_byname(ualg->alg_name, 1);
 	if (!algo)
 		return -ENOSYS;
-	if (ualg->alg_trunc_len > algo->uinfo.auth.icv_fullbits)
+	if ((ualg->alg_trunc_len / 8) > MAX_AH_AUTH_LEN ||
+	    ualg->alg_trunc_len > algo->uinfo.auth.icv_fullbits)
 		return -EINVAL;
 	*props = algo->desc.sadb_alg_id;