[PATCH 03/38] crypto: drbg - Fix ineffective sanity check

[Eric Biggers]

Fix drbg_healthcheck_sanity() to correctly check the return value of
drbg_generate().  drbg_generate() returns 0 on success, or a negative
errno value on failure.  drbg_healthcheck_sanity() incorrectly assumed
that it returned a positive value on success.

This didn't make the sanity check fail, but it made it ineffective.

Fixes: cde001e4c3c3 ("crypto: rng - RNGs must return 0 in success case")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 crypto/drbg.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index de4c69032155..f23b431bd490 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1735,11 +1735,10 @@ static int drbg_kcapi_seed(struct crypto_rng *tfm,
  * Note 2: There is no sensible way of testing the reseed counter
  * enforcement, so skip it.
  */
 static inline int __init drbg_healthcheck_sanity(void)
 {
-	int len = 0;
 #define OUTBUFLEN 16
 	unsigned char buf[OUTBUFLEN];
 	struct drbg_state *drbg = NULL;
 	int ret;
 	int rc = -EFAULT;
@@ -1780,15 +1779,15 @@ static inline int __init drbg_healthcheck_sanity(void)
 
 	max_addtllen = drbg_max_addtl(drbg);
 	max_request_bytes = drbg_max_request_bytes(drbg);
 	drbg_string_fill(&addtl, buf, max_addtllen + 1);
 	/* overflow addtllen with additional info string */
-	len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
-	BUG_ON(0 < len);
+	ret = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
+	BUG_ON(ret == 0);
 	/* overflow max_bits */
-	len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
-	BUG_ON(0 < len);
+	ret = drbg_generate(drbg, buf, max_request_bytes + 1, NULL);
+	BUG_ON(ret == 0);
 
 	/* overflow max addtllen with personalization string */
 	ret = drbg_seed(drbg, &addtl, false);
 	BUG_ON(0 == ret);
 	/* all tests passed */
-- 
2.53.0