filter: fix sk_filter rcu handling
Pavel Emelyanov tried to fix a race between sk_filter_(de|at)tach and
sk_clone() in commit 47e958eac280c263397
Problem is we can have several clones sharing a common sk_filter, and
these clones might want to sk_filter_attach() their own filters at the
same time, and can overwrite old_filter->rcu, corrupting RCU queues.
We can not use filter->rcu without being sure no other thread could do
the same thing.
Switch code to a more conventional ref-counting technique : Do the
atomic decrement immediately and queue one rcu call back when last
reference is released.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index a6338d0..659d968d9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1155,6 +1155,8 @@
/* Initialise core socket variables */
extern void sock_init_data(struct socket *sock, struct sock *sk);
+extern void sk_filter_release_rcu(struct rcu_head *rcu);
+
/**
* sk_filter_release - release a socket filter
* @fp: filter to remove
@@ -1165,7 +1167,7 @@
static inline void sk_filter_release(struct sk_filter *fp)
{
if (atomic_dec_and_test(&fp->refcnt))
- kfree(fp);
+ call_rcu_bh(&fp->rcu, sk_filter_release_rcu);
}
static inline void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
diff --git a/net/core/filter.c b/net/core/filter.c
index c1ee800..ae21a0d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -589,23 +589,16 @@
EXPORT_SYMBOL(sk_chk_filter);
/**
- * sk_filter_rcu_release - Release a socket filter by rcu_head
+ * sk_filter_release_rcu - Release a socket filter by rcu_head
* @rcu: rcu_head that contains the sk_filter to free
*/
-static void sk_filter_rcu_release(struct rcu_head *rcu)
+void sk_filter_release_rcu(struct rcu_head *rcu)
{
struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
- sk_filter_release(fp);
+ kfree(fp);
}
-
-static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp)
-{
- unsigned int size = sk_filter_len(fp);
-
- atomic_sub(size, &sk->sk_omem_alloc);
- call_rcu_bh(&fp->rcu, sk_filter_rcu_release);
-}
+EXPORT_SYMBOL(sk_filter_release_rcu);
/**
* sk_attach_filter - attach a socket filter
@@ -649,7 +642,7 @@
rcu_assign_pointer(sk->sk_filter, fp);
if (old_fp)
- sk_filter_delayed_uncharge(sk, old_fp);
+ sk_filter_uncharge(sk, old_fp);
return 0;
}
EXPORT_SYMBOL_GPL(sk_attach_filter);
@@ -663,7 +656,7 @@
sock_owned_by_user(sk));
if (filter) {
rcu_assign_pointer(sk->sk_filter, NULL);
- sk_filter_delayed_uncharge(sk, filter);
+ sk_filter_uncharge(sk, filter);
ret = 0;
}
return ret;