crypto: rng - RNGs must return 0 in success case

Change the RNGs to always return 0 in success case.

This patch ensures that seqiv.c works with RNGs other than krng. seqiv
expects that any return code other than 0 is an error. Without the
patch, rfc4106(gcm(aes)) will not work when using a DRBG or an ANSI
X9.31 RNG.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 12 insertions, 4 deletions

diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index 6f5bebc9bf01..765fe7609348 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -210,7 +210,11 @@ static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
                 byte_count = DEFAULT_BLK_SZ;
         }
 
-        err = byte_count;
+        /*
+         * Return 0 in case of success as mandated by the kernel
+         * crypto API interface definition.
+         */
+        err = 0;
 
         dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
                 byte_count, ctx);
diff --git a/crypto/drbg.c b/crypto/drbg.c
index 56c1d7ec3d9e..b69409cb7e6a 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1280,7 +1280,7 @@ static void drbg_restore_shadow(struct drbg_state *drbg,
  *        as defined in SP800-90A. The additional input is mixed into
  *        the state in addition to the pulled entropy.
  *
- * return: generated number of bytes
+ * return: 0 when all bytes are generated; < 0 in case of an error
  */
 static int drbg_generate(struct drbg_state *drbg,
                          unsigned char *buf, unsigned int buflen,
@@ -1419,6 +1419,11 @@ static int drbg_generate(struct drbg_state *drbg,
         }
 #endif
 
+        /*
+         * All operations were successful, return 0 as mandated by
+         * the kernel crypto API interface.
+         */
+        len = 0;
 err:
         shadow->d_ops->crypto_fini(shadow);
         drbg_restore_shadow(drbg, &shadow);
diff --git a/include/crypto/rng.h b/include/crypto/rng.h
index a16fb10142bf..6e28ea5be9f1 100644
--- a/include/crypto/rng.h
+++ b/include/crypto/rng.h
@@ -103,8 +103,7 @@ static inline void crypto_free_rng(struct crypto_rng *tfm)
  * This function fills the caller-allocated buffer with random numbers using the
  * random number generator referenced by the cipher handle.
  *
- * Return: > 0 function was successful and returns the number of generated
- *         bytes; < 0 if an error occurred
+ * Return: 0 function was successful; < 0 if an error occurred
  */
 static inline int crypto_rng_get_bytes(struct crypto_rng *tfm,
                                        u8 *rdata, unsigned int dlen)