From: Jason A. Donenfeld Date: Fri, 24 Dec 2021 18:17:58 +0000 (+0100) Subject: random: do not sign extend bytes for rotation when mixing X-Git-Tag: v4.19.249~184 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7c03c22e91dc89d7adc4042be93c33a04d6d1797;p=thirdparty%2Fkernel%2Fstable.git random: do not sign extend bytes for rotation when mixing commit 0d9488ffbf2faddebc6bac055bfa6c93b94056a3 upstream. By using `char` instead of `unsigned char`, certain platforms will sign extend the byte when `w = rol32(*bytes++, input_rotate)` is called, meaning that bit 7 is overrepresented when mixing. This isn't a real problem (unless the mixer itself is already broken) since it's still invertible, but it's not quite correct either. Fix this by using an explicit unsigned type. Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/char/random.c b/drivers/char/random.c index 8fc1a1e0d6813..e5dda790040cc 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -549,7 +549,7 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in, unsigned long i, tap1, tap2, tap3, tap4, tap5; int input_rotate; int wordmask = r->poolinfo->poolwords - 1; - const char *bytes = in; + const unsigned char *bytes = in; __u32 w; tap1 = r->poolinfo->tap1;