[PATCH] DRBG: fix failure of generating multiple of 2**16 bytes

[Stephan Mueller <smueller@chronox.de>]

The function drbg_generate_long slices the request into 2**16 byte
or smaller chunks. However, the loop, however invokes the random number
generation function with zero bytes when the request size is a multiple
of 2**16 bytes. The fix prevents zero bytes requests.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 crypto/drbg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index ff975d9..7894db9 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1500,7 +1500,7 @@ static int drbg_generate_long(struct drbg_state *drbg,
 		if (0 >= tmplen)
 			return tmplen;
 		len += tmplen;
-	} while (slice > 0);
+	} while (slice > 0 && (len < buflen));
 	return len;
 }
 
-- 
1.9.3