This is a note to let you know that I've just added the patch titled
ipv4: fix dst race in sk_dst_get()
to the 3.10-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:
ipv4-fix-dst-race-in-sk_dst_get.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From foo@baz Sat Jul 26 10:03:51 PDT 2014
From: Eric Dumazet <[email protected]>
Date: Tue, 24 Jun 2014 10:05:11 -0700
Subject: ipv4: fix dst race in sk_dst_get()
From: Eric Dumazet <[email protected]>
[ Upstream commit f88649721268999bdff09777847080a52004f691 ]
When IP route cache had been removed in linux-3.6, we broke assumption
that dst entries were all freed after rcu grace period. DST_NOCACHE
dst were supposed to be freed from dst_release(). But it appears
we want to keep such dst around, either in UDP sockets or tunnels.
In sk_dst_get() we need to make sure dst refcount is not 0
before incrementing it, or else we might end up freeing a dst
twice.
DST_NOCACHE set on a dst does not mean this dst can not be attached
to a socket or a tunnel.
Then, before actual freeing, we need to observe a rcu grace period
to make sure all other cpus can catch the fact the dst is no longer
usable.
Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: Dormando <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
include/net/sock.h | 4 ++--
net/core/dst.c | 16 +++++++++++-----
2 files changed, 13 insertions(+), 7 deletions(-)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1727,8 +1727,8 @@ sk_dst_get(struct sock *sk)
rcu_read_lock();
dst = rcu_dereference(sk->sk_dst_cache);
- if (dst)
- dst_hold(dst);
+ if (dst && !atomic_inc_not_zero(&dst->__refcnt))
+ dst = NULL;
rcu_read_unlock();
return dst;
}
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -267,6 +267,15 @@ again:
}
EXPORT_SYMBOL(dst_destroy);
+static void dst_destroy_rcu(struct rcu_head *head)
+{
+ struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
+
+ dst = dst_destroy(dst);
+ if (dst)
+ __dst_free(dst);
+}
+
void dst_release(struct dst_entry *dst)
{
if (dst) {
@@ -274,11 +283,8 @@ void dst_release(struct dst_entry *dst)
newrefcnt = atomic_dec_return(&dst->__refcnt);
WARN_ON(newrefcnt < 0);
- if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) {
- dst = dst_destroy(dst);
- if (dst)
- __dst_free(dst);
- }
+ if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt)
+ call_rcu(&dst->rcu_head, dst_destroy_rcu);
}
}
EXPORT_SYMBOL(dst_release);
Patches currently in stable-queue which might be from [email protected] are
queue-3.10/appletalk-fix-socket-referencing-in-skb.patch
queue-3.10/8021q-fix-a-potential-memory-leak.patch
queue-3.10/ipv4-fix-dst-race-in-sk_dst_get.patch
queue-3.10/tcp-fix-tcp_match_skb_to_sack-for-unaligned-sack-at-end-of-an-skb.patch
queue-3.10/ipv4-irq-safe-sk_dst_set-and-ipv4_sk_update_pmtu-fix.patch
queue-3.10/net-fix-sparse-warning-in-sk_dst_set.patch
queue-3.10/bnx2x-fix-possible-panic-under-memory-stress.patch
queue-3.10/ipv4-fix-buffer-overflow-in-ip_options_compile.patch
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