3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Theodore Ts'o tytso@mit.edu
commit 9f886f4d1d292442b2f22a0a33321eae821bde40 upstream.
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 tytso@mit.edu Reported-by: Chen Feng puck.chen@hisilicon.com Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -704,7 +704,7 @@ retry:
static void 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;
/* Cap the value to avoid overflows */ nbits = min(nbits, nbits_max);