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authorTom Herbert <tom@herbertland.com>2015-08-05 09:39:27 -0700
committerDavid S. Miller <davem@davemloft.net>2015-08-07 15:56:56 -0700
commit10e4ea75149d11883a9e04c3b32ee1d7600d481e (patch)
tree4cf760912a8c9e3447619d6cdaeeac0835e9eaae
parente05176a3283822bd32a1f3d929ce2050232299a8 (diff)
net: Fix race condition in store_rps_map
There is a race condition in store_rps_map that allows jump label count in rps_needed to go below zero. This can happen when concurrently attempting to set and a clear map. Scenario: 1. rps_needed count is zero 2. New map is assigned by setting thread, but rps_needed count _not_ yet incremented (rps_needed count still zero) 2. Map is cleared by second thread, old_map set to that just assigned 3. Second thread performs static_key_slow_dec, rps_needed count now goes negative Fix is to increment or decrement rps_needed under the spinlock. Signed-off-by: Tom Herbert <tom@herbertland.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/net-sysfs.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 194c1d03b2b3..39ec6949c1e6 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -726,14 +726,17 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
old_map = rcu_dereference_protected(queue->rps_map,
lockdep_is_held(&rps_map_lock));
rcu_assign_pointer(queue->rps_map, map);
- spin_unlock(&rps_map_lock);
if (map)
static_key_slow_inc(&rps_needed);
- if (old_map) {
- kfree_rcu(old_map, rcu);
+ if (old_map)
static_key_slow_dec(&rps_needed);
- }
+
+ spin_unlock(&rps_map_lock);
+
+ if (old_map)
+ kfree_rcu(old_map, rcu);
+
free_cpumask_var(mask);
return len;
}