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authorGeorge Spelvin <linux@horizon.com>2015-02-07 00:32:06 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-09 12:28:42 -0800
commit19acc77a36970958a4a0e4daeb2c8cb2aab0ffd4 (patch)
tree97c4a18e6a60024256fc92fffed0cae95d0b4ef7 /drivers/char
parentbfa76d49576599a4b9f9b7a71f23d73d6dcff735 (diff)
random: Fix fast_mix() function
There was a bad typo in commit 43759d4f429c ("random: use an improved fast_mix() function") and I didn't notice because it "looked right", so I saw what I expected to see when I reviewed it. Only months later did I look and notice it's not the Threefish-inspired mix function that I had designed and optimized. Mea Culpa. Each input bit still has a chance to affect each output bit, and the fast pool is spilled *long* before it fills, so it's not a total disaster, but it's definitely not the intended great improvement. I'm still working on finding better rotation constants. These are good enough, but since it's unrolled twice, it's possible to get better mixing for free by using eight different constants rather than repeating the same four. Signed-off-by: George Spelvin <linux@horizon.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org # v3.16+ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 04645c09fe5..9cd6968e2f9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -569,19 +569,19 @@ static void fast_mix(struct fast_pool *f)
__u32 c = f->pool[2], d = f->pool[3];
a += b; c += d;
- b = rol32(a, 6); d = rol32(c, 27);
+ b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
- b = rol32(a, 16); d = rol32(c, 14);
+ b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
a += b; c += d;
- b = rol32(a, 6); d = rol32(c, 27);
+ b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
- b = rol32(a, 16); d = rol32(c, 14);
+ b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
f->pool[0] = a; f->pool[1] = b;