This is a note to let you know that I've just added the patch titled
random32: fix off-by-one in seeding requirement
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random32-fix-off-by-one-in-seeding-requirement.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 02638b50e8249d902d2ac84477e80e501c7c31cc Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman@xxxxxxxxxx>
Date: Mon, 11 Nov 2013 12:20:32 +0100
Subject: random32: fix off-by-one in seeding requirement
From: Daniel Borkmann <dborkman@xxxxxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Signed-off-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/random.h | 6 +++---
lib/random32.c | 14 +++++++-------
2 files changed, 10 insertions(+), 10 deletions(-)
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -87,9 +87,9 @@ static inline void prandom32_seed(struct
{
u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
- state->s1 = __seed(i, 1);
- state->s2 = __seed(i, 7);
- state->s3 = __seed(i, 15);
+ state->s1 = __seed(i, 2);
+ state->s2 = __seed(i, 8);
+ state->s3 = __seed(i, 16);
}
#ifdef CONFIG_ARCH_RANDOM
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -92,7 +92,7 @@ void srandom32(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(srandom32);
@@ -109,9 +109,9 @@ static int __init random32_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" */
prandom32(state);
@@ -138,9 +138,9 @@ static int __init random32_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 */
prandom32(state);
Patches currently in stable-queue which might be from dborkman@xxxxxxxxxx are
queue-3.4/random32-fix-off-by-one-in-seeding-requirement.patch
queue-3.4/packet-fix-use-after-free-race-in-send-path-when-dev-is-released.patch
queue-3.4/af_packet-block-bh-in-prb_shutdown_retire_blk_timer.patch
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