netdev - [PATCH net-next 2/2] net_sched: sfq: always randomize hash perturbation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 04 Jan 2012 17:23:01 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next 2/2] net_sched: sfq: always randomize hash
 perturbation

SFQ q->perturbation is used in sfq_hash() as an input to Jenkins hash.

We currently randomize this 32bit value only if a perturbation timer is
setup.

Its much better to always initialize it to defeat attackers, or else
they can predict very well what kind of packets they have to forge to
hit a particular flow.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/sched/sch_sfq.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 465af66..a1cb00e 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -591,12 +591,12 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
 	q->cur_depth = 0;
 	q->tail = NULL;
 	q->divisor = SFQ_DEFAULT_HASH_DIVISOR;
-	if (opt == NULL) {
-		q->quantum = psched_mtu(qdisc_dev(sch));
-		q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
-		q->perturb_period = 0;
-		q->perturbation = net_random();
-	} else {
+	q->quantum = psched_mtu(qdisc_dev(sch));
+	q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
+	q->perturb_period = 0;
+	q->perturbation = net_random();
+
+	if (opt) {
 		int err = sfq_change(sch, opt);
 		if (err)
 			return err;


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html