Messages in this thread Patch in this message | | | From | "Jason A. Donenfeld" <> | Subject | [PATCH] random: do not sign extend bytes for rotation when mixing | Date | Sat, 25 Dec 2021 02:00:11 +0100 |
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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> --- 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 99cce575a79c..82db125aaed7 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -546,7 +546,7 @@ 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; -- 2.34.1
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