From 9f886f4d1d292442b2f22a0a33321eae821bde40 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sat, 25 Feb 2017 18:21:33 -0400 Subject: [PATCH] random: use a tighter cap in credit_entropy_bits_safe() This fixes a harmless UBSAN where root could potentially end up causing an overflow while bumping the entropy_total field (which is ignored once the entropy pool has been initialized, and this generally is completed during the boot sequence). This is marginal for the stable kernel series, but it's a really trivial patch, and it fixes UBSAN warning that might cause security folks to get overly excited for no reason. Signed-off-by: Theodore Ts'o Reported-by: Chen Feng Cc: stable@vger.kernel.org --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index e5b3d3b..11c23ca 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -732,7 +732,7 @@ retry: static int credit_entropy_bits_safe(struct entropy_store *r, int nbits) { - const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1)); + const int nbits_max = r->poolinfo->poolwords * 32; if (nbits < 0) return -EINVAL; -- 2.7.4