crypto: asymmetric_keys - prevent overflow in asymmetric_key_generate_id

[ Upstream commit df0845cf447ae1556c3440b8b155de0926cbaa56 ]

Use check_add_overflow() to guard against potential integer overflows
when adding the binary blob lengths and the size of an asymmetric_key_id
structure and return ERR_PTR(-EOVERFLOW) accordingly. This prevents a
possible buffer overflow when copying data from potentially malicious
X.509 certificate fields that can be arbitrarily large, such as ASN.1
INTEGER serial numbers, issuer names, etc.

Fixes: 7901c1a8ef ("KEYS: Implement binary asymmetric key ID handling")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

crypto/asymmetric_keys/asymmetric_type.c

@@ -11,6 +11,7 @@
 #include <crypto/public_key.h>
 #include <linux/seq_file.h>
 #include <linux/module.h>
+#include <linux/overflow.h>
 #include <linux/slab.h>
 #include <linux/ctype.h>
 #include <keys/system_keyring.h>
@@ -151,12 +152,17 @@ struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
 						     size_t len_2)
 {
 	struct asymmetric_key_id *kid;
+	size_t kid_sz;
+	size_t len;
 
-	kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
-		      GFP_KERNEL);
+	if (check_add_overflow(len_1, len_2, &len))
+		return ERR_PTR(-EOVERFLOW);
+	if (check_add_overflow(sizeof(struct asymmetric_key_id), len, &kid_sz))
+		return ERR_PTR(-EOVERFLOW);
+	kid = kmalloc(kid_sz, GFP_KERNEL);
 	if (!kid)
 		return ERR_PTR(-ENOMEM);
-	kid->len = len_1 + len_2;
+	kid->len = len;
 	memcpy(kid->data, val_1, len_1);
 	memcpy(kid->data + len_1, val_2, len_2);
 	return kid;