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authorDaniel Borkmann <dborkman@redhat.com>2013-11-11 12:20:32 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 07:29:24 -0800
commite29507fecb79c00ae76f9ef626d282af8b1f4225 (patch)
tree8317f8069bf13d75975db813c577debf12da1cb5 /lib
parente688cd4d32cfbf0b5198ba95da428038e907e633 (diff)
downloadlinux-linaro-stable-e29507fecb79c00ae76f9ef626d282af8b1f4225.tar.gz
random32: fix off-by-one in seeding requirement
[ Upstream commit 51c37a70aaa3f95773af560e6db3073520513912 ] For properly initialising the Tausworthe generator [1], we have a strict seeding requirement, that is, s1 > 1, s2 > 7, s3 > 15. Commit 697f8d0348 ("random32: seeding improvement") introduced a __seed() function that imposes boundary checks proposed by the errata paper [2] to properly ensure above conditions. However, we're off by one, as the function is implemented as: "return (x < m) ? x + m : x;", and called with __seed(X, 1), __seed(X, 7), __seed(X, 15). Thus, an unwanted seed of 1, 7, 15 would be possible, whereas the lower boundary should actually be of at least 2, 8, 16, just as GSL does. Fix this, as otherwise an initialization with an unwanted seed could have the effect that Tausworthe's PRNG properties cannot not be ensured. Note that this PRNG is *not* used for cryptography in the kernel. [1] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps [2] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps Joint work with Hannes Frederic Sowa. Fixes: 697f8d0348a6 ("random32: seeding improvement") Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/random32.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/lib/random32.c b/lib/random32.c
index 52280d5526be..01e8890d1089 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -141,7 +141,7 @@ void prandom_seed(u32 entropy)
*/
for_each_possible_cpu (i) {
struct rnd_state *state = &per_cpu(net_rand_state, i);
- state->s1 = __seed(state->s1 ^ entropy, 1);
+ state->s1 = __seed(state->s1 ^ entropy, 2);
}
}
EXPORT_SYMBOL(prandom_seed);
@@ -158,9 +158,9 @@ static int __init prandom_init(void)
struct rnd_state *state = &per_cpu(net_rand_state,i);
#define LCG(x) ((x) * 69069) /* super-duper LCG */
- state->s1 = __seed(LCG(i + jiffies), 1);
- state->s2 = __seed(LCG(state->s1), 7);
- state->s3 = __seed(LCG(state->s2), 15);
+ state->s1 = __seed(LCG(i + jiffies), 2);
+ state->s2 = __seed(LCG(state->s1), 8);
+ state->s3 = __seed(LCG(state->s2), 16);
/* "warm it up" */
prandom_u32_state(state);
@@ -187,9 +187,9 @@ static int __init prandom_reseed(void)
u32 seeds[3];
get_random_bytes(&seeds, sizeof(seeds));
- state->s1 = __seed(seeds[0], 1);
- state->s2 = __seed(seeds[1], 7);
- state->s3 = __seed(seeds[2], 15);
+ state->s1 = __seed(seeds[0], 2);
+ state->s2 = __seed(seeds[1], 8);
+ state->s3 = __seed(seeds[2], 16);
/* mix it in */
prandom_u32_state(state);