| From foo@baz Thu Jun 16 06:59:24 PM CEST 2022 |
| From: "Jason A. Donenfeld" <Jason@zx2c4.com> |
| Date: Fri, 24 Dec 2021 19:17:58 +0100 |
| Subject: random: do not sign extend bytes for rotation when mixing |
| |
| From: "Jason A. Donenfeld" <Jason@zx2c4.com> |
| |
| 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 <Jason@zx2c4.com> |
| 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 |
| @@ -550,7 +550,7 @@ static void _mix_pool_bytes(struct entro |
| 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; |
