netdev - [PATCH net-next-2.6] sfq: fix slot_dequeue

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Date:	Thu, 30 Dec 2010 16:02:48 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Jarek Poplawski <jarkao2@...il.com>
Subject: [PATCH net-next-2.6] sfq: fix slot_dequeue_head()

Le mercredi 22 décembre 2010 à 07:32 +0000, Jarek Poplawski a écrit :
> > Also, slot_dequeue_tail() should make sure slot skb chain is correctly
> > terminated, or sfq_dump_class_stats() can access freed skbs.
> 
> ...and a good hint for code reusing ;-)

Yes, and of course same fix is needed in slot_dequeue_head(), as further
testing on my side made it pretty clear.

I was adding possibility to have more packets queued in SFQ (more
packets than max number of flows) and got unexpected crashes.

Reverting to net-next-2.6, I still got crashes. Oops.

[PATCH net-next-2.6] sfq: fix slot_dequeue_head()

slot_dequeue_head() should make sure slot skb chain is correct in both
ways, or we can crash if all possible flows are in use.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Cc: Jarek Poplawski <jarkao2@...il.com>
---
 net/sched/sch_sfq.c |    1 +
 1 files changed, 1 insertion(+)

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 6a2f88f..3977e56 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -292,6 +292,7 @@ static inline struct sk_buff *slot_dequeue_head(struct sfq_slot *slot)
 	struct sk_buff *skb = slot->skblist_next;
 
 	slot->skblist_next = skb->next;
+	skb->next->prev = (struct sk_buff *)slot;
 	skb->next = skb->prev = NULL;
 	return skb;
 }


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