linux-kernel - [PATCH 1/1] crypto: If two strings are exact match, they must have same length.

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Date:   Tue, 21 Mar 2017 16:40:40 -0500
From:   Ming Ma <mingma@...ron.com>
To:     <herbert@...dor.apana.org.au>, <davem@...emloft.net>
CC:     <linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ming Ma <mingma@...ron.com>
Subject: [PATCH 1/1] crypto: If two strings are exact match, they must have same length.

When both "crct10dif-pclmul" algorithm and "crct10dif-generic" algorithm
exist in crypto_alg_list, "crct10dif-pclmul" should be selected, since it
has higher priority than "crct10dif-generic". However, both algorithms
have the same cra_name "crct10dif". If we use "crct10dif" to find a
matched algorithm in crypto_alg_list, it's possible "crct10dif-generic" is
selected, because the code calls strcmp to decide if two string are exact
match, but doesn't check if two strings have the same length.

exact = !strcmp(q->cra_driver_name, name);

So ,if "crct10dif-generic" is in front of "crct10dif-pclmul" in
crypto_alg_list, it will be picked as the matched algorithm, even if it has
lower priority than "crct10dif-pclmul".
Signed-off-by: Ming Ma <mingma@...ron.com>
---
 crypto/api.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crypto/api.c b/crypto/api.c
index b16ce16..5b3d45a 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -76,7 +76,8 @@ static struct crypto_alg *__crypto_alg_lookup(const char *name, u32 type,
 		    ((struct crypto_larval *)q)->mask != mask)
 			continue;
 
-		exact = !strcmp(q->cra_driver_name, name);
+		exact = (strlen(name) == strlen(q->cra_driver_name)) &&
+				!strcmp(q->cra_driver_name, name);
 		fuzzy = !strcmp(q->cra_name, name);
 		if (!exact && !(fuzzy && q->cra_priority > best))
 			continue;
-- 
2.4.11