From d8a7dd7122d411662e7ccf9986070fbe2ac2aeb2 Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Tue, 17 Sep 2013 08:33:11 -0400 Subject: crypto: ansi_cprng - Fix off by one error in non-block size request commit 714b33d15130cbb5ab426456d4e3de842d6c5b8a upstream. 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 Reported-by: Stephan Mueller CC: Stephan Mueller CC: Petr Matousek CC: Herbert Xu CC: "David S. Miller" Signed-off-by: Herbert Xu Cc: Luis Henriques Signed-off-by: Greg Kroah-Hartman --- 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 c0bb3778f1a..666f1962a16 100644 --- a/crypto/ansi_cprng.c +++ b/crypto/ansi_cprng.c @@ -230,11 +230,11 @@ remainder: */ 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; } -- cgit v1.2.3