Re: [PATCH v2] random: avoid mis-detecting a slow counter as a cycle counter
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: 2022-04-21 23:40:41
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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: 2022-04-21 23:40:41
Also in:
lkml
Hi Eric, Thanks. This looks better. On Thu, Apr 21, 2022 at 04:31:52PM -0700, Eric Biggers wrote:
Therefore, increase the number of counter comparisons from 1 to 3, to
greatly reduce the rate of false positive cycle counter detections.
+ for (i = 0; i < 3; i++) {
+ unsigned long entropy = random_get_entropy();Wondering: why do you do 3 comparisons rather than 2? What does 3 get you that 2 doesn't already? I thought the only real requirement was that in the event where (a)!=(b), (b) is read as meaningfully close as possible to when the counter changes. Jason