[PATCH 6.18,6.12,6.6,6.1,5.15,5.10] crypto: drbg - Fix ineffective sanity check

[Eric Biggers <ebiggers@kernel.org>]

commit 040ad83b0e8aa065fd2fc641cacba8491a8b186d upstream.

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@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

This commit doesn't matter for anything other than certification.  But
it did have 'Cc stable' on it, and it failed to apply due to a trivial
conflict.  So it might as well be backported as intended.

 crypto/drbg.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index dc8996789da6..51c36cfa8eff 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1986,7 +1986,6 @@ static int drbg_kcapi_seed(struct crypto_rng *tfm,
  */
 static inline int __init drbg_healthcheck_sanity(void)
 {
-	int len = 0;
 #define OUTBUFLEN 16
 	unsigned char buf[OUTBUFLEN];
 	struct drbg_state *drbg = NULL;
@@ -2030,12 +2029,12 @@ 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 additonal info string */
-	len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
-	BUG_ON(0 < len);
+	/* overflow addtllen with additional info string */
+	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);

base-commit: 725bd2f3c81d54edccb66fead01d4c0c222e2231
-- 
2.56.0