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random: do not sign extend bytes for rotation when mixing

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commit 0d9488ffbf 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>
This commit is contained in:
Jason A. Donenfeld 2021-12-24 19:17:58 +01:00 committed by Greg Kroah-Hartman
parent 685200b076
commit 2bfdf588a8
1 changed files with 1 additions and 1 deletions
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2
drivers/char/random.c
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@ -547,7 +547,7 @@ 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;