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Date: Tue, 28 Jul 2015 11:43:37 +0200 From: Jiri Slaby <jslaby@...e.cz> To: stable@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Julian Anastasov <ja@....bg>, Eric Dumazet <eric.dumazet@...il.com>, Ying Xue <ying.xue@...driver.com>, "David S. Miller" <davem@...emloft.net>, Jiri Slaby <jslaby@...e.cz> Subject: [PATCH 3.12 083/124] neigh: do not modify unlinked entries From: Julian Anastasov <ja@....bg> 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit 2c51a97f76d20ebf1f50fef908b986cb051fdff9 ] The lockless lookups can return entry that is unlinked. Sometimes they get reference before last neigh_cleanup_and_release, sometimes they do not need reference. Later, any modification attempts may result in the following problems: 1. entry is not destroyed immediately because neigh_update can start the timer for dead entry, eg. on change to NUD_REACHABLE state. As result, entry lives for some time but is invisible and out of control. 2. __neigh_event_send can run in parallel with neigh_destroy while refcnt=0 but if timer is started and expired refcnt can reach 0 for second time leading to second neigh_destroy and possible crash. Thanks to Eric Dumazet and Ying Xue for their work and analyze on the __neigh_event_send change. Fixes: 767e97e1e0db ("neigh: RCU conversion of struct neighbour") Fixes: a263b3093641 ("ipv4: Make neigh lookups directly in output packet path.") Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().") Cc: Eric Dumazet <eric.dumazet@...il.com> Cc: Ying Xue <ying.xue@...driver.com> Signed-off-by: Julian Anastasov <ja@....bg> Acked-by: Eric Dumazet <edumazet@...gle.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Jiri Slaby <jslaby@...e.cz> --- net/core/neighbour.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 467e3e071832..7453923dc507 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -971,6 +971,8 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb) rc = 0; if (neigh->nud_state & (NUD_CONNECTED | NUD_DELAY | NUD_PROBE)) goto out_unlock_bh; + if (neigh->dead) + goto out_dead; if (!(neigh->nud_state & (NUD_STALE | NUD_INCOMPLETE))) { if (neigh->parms->mcast_probes + neigh->parms->app_probes) { @@ -1024,6 +1026,13 @@ out_unlock_bh: write_unlock(&neigh->lock); local_bh_enable(); return rc; + +out_dead: + if (neigh->nud_state & NUD_STALE) + goto out_unlock_bh; + write_unlock_bh(&neigh->lock); + kfree_skb(skb); + return 1; } EXPORT_SYMBOL(__neigh_event_send); @@ -1087,6 +1096,8 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, if (!(flags & NEIGH_UPDATE_F_ADMIN) && (old & (NUD_NOARP | NUD_PERMANENT))) goto out; + if (neigh->dead) + goto out; if (!(new & NUD_VALID)) { neigh_del_timer(neigh); -- 2.4.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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