From 714b33d15130cbb5ab426456d4e3de842d6c5b8a Mon Sep 17 00:00:00 2001
From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 17 Sep 2013 08:33:11 -0400
Subject: [PATCH] crypto: ansi_cprng - Fix off by one error in non-block size
request
Stephan Mueller reported to me recently a error in random number generation in
the ansi cprng. If several small requests are made that are less than the
instances block size, the remainder for loop code doesn't increment
rand_data_valid in the last iteration, meaning that the last bytes in the
rand_data buffer gets reused on the subsequent smaller-than-a-block request for
random data.
The fix is pretty easy, just re-code the for loop to make sure that
rand_data_valid gets incremented appropriately
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Stephan Mueller <stephan.mueller@atsec.com>
CC: Stephan Mueller <stephan.mueller@atsec.com>
CC: Petr Matousek <pmatouse@redhat.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
crypto/ansi_cprng.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index c0bb3778f1ae0..666f1962a160f 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -230,11 +230,11 @@ static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
*/
if (byte_count < DEFAULT_BLK_SZ) {
empty_rbuf:
- for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
- ctx->rand_data_valid++) {
+ while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
*ptr = ctx->rand_data[ctx->rand_data_valid];
ptr++;
byte_count--;
+ ctx->rand_data_valid++;
if (byte_count == 0)
goto done;
}
--
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