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  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 11 Aug 2014 19:41:06 -0300
From:	Marcelo Ricardo Leitner <mleitner@...hat.com>
To:	davem@...emloft.net
Cc:	hannes@...hat.com, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: [PATCH stable 3.4 2/2] ipv4: avoid parallel route cache gc executions

When rt_intern_hash() has to deal with neighbour cache overflowing,
it triggers the route cache garbage collector in an attempt to free
some references on neighbour entries.

Such call cannot be done async but should also not run in parallel with
an already-running one, so that they don't collapse fighting over the
hash lock entries.

This patch thus blocks parallel executions by ignoring the call if
garbage collector is already running on another CPU.

We don't use a spinlock for it because now it runs on a work queue and
we want it to be schedulable in-between the hash indexes.

Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com>
Cc: Hannes Frederic Sowa <hannes@...hat.com>
---
 net/ipv4/route.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 2ad1cdb2c9e45f5ec5a6c1fa9b781657b1c292ec..68153bb86b62b500febd2a134f71348fa78295d9 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -986,6 +986,7 @@ static void __do_rt_garbage_collect(int elasticity, int min_interval)
 	static unsigned long last_gc;
 	static int rover;
 	static int equilibrium;
+	static int rt_gc_barrier;
 	struct rtable *rth;
 	struct rtable __rcu **rthp;
 	unsigned long now = jiffies;
@@ -999,6 +1000,12 @@ static void __do_rt_garbage_collect(int elasticity, int min_interval)
 
 	RT_CACHE_STAT_INC(gc_total);
 
+	if (cmpxchg(&rt_gc_barrier, 0, 1) != 0) {
+		/* busy */
+		RT_CACHE_STAT_INC(gc_ignored);
+		return;
+	}
+
 	if (now - last_gc < min_interval &&
 	    entries < ip_rt_max_size) {
 		RT_CACHE_STAT_INC(gc_ignored);
@@ -1089,6 +1096,7 @@ static void __do_rt_garbage_collect(int elasticity, int min_interval)
 	if (net_ratelimit())
 		pr_warn("dst cache overflow\n");
 	RT_CACHE_STAT_INC(gc_dst_overflow);
+	rt_gc_barrier = 0;
 	return;
 
 work_done:
@@ -1097,7 +1105,9 @@ work_done:
 	    dst_entries_get_fast(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh ||
 	    dst_entries_get_slow(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh)
 		expire = ip_rt_gc_timeout;
-out:	return;
+out:
+	rt_gc_barrier = 0;
+	return;
 }
 
 static void __rt_garbage_collect(struct work_struct *w)
-- 
1.9.3

--
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

Powered by blists - more mailing lists