Patchwork net: fix secpath kmemleak

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Submitter Eric Dumazet
Date Oct. 22, 2012, 7:03 p.m.
Message ID <1350932620.8609.1142.camel@edumazet-glaptop>
Download mbox | patch
Permalink /patch/193257/
State Accepted
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - Oct. 22, 2012, 7:03 p.m.
From: Eric Dumazet <edumazet@google.com>

Mike Kazantsev found 3.5 kernels and beyond were leaking memory,
and tracked the faulty commit to a1c7fff7e18f59e (net:
netdev_alloc_skb() use build_skb()

While this commit seems fine, it uncovered a bug introduced
in commit bad43ca8325 (net: introduce skb_try_coalesce()), in function
kfree_skb_partial() :

If head is stolen, we free the sk_buff,
without removing references on secpath (skb->sp).

So IPsec + IP defrag/reassembly (using skb coalescing), or
TCP coalescing could leak secpath objects.

Fix this bug by calling skb_release_head_state(skb) to properly
release all possible references to linked objects.

Reported-by: Mike Kazantsev <mk.fraggod@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Bisected-by: Mike Kazantsev <mk.fraggod@gmail.com>
Tested-by: Mike Kazantsev <mk.fraggod@gmail.com>
---
It seems TCP stack could immediately release secpath references instead
of waiting skb are eaten by consumer, thats will be a followup patch.

 net/core/skbuff.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)




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David Miller - Oct. 22, 2012, 7:17 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 22 Oct 2012 21:03:40 +0200

> From: Eric Dumazet <edumazet@google.com>
> 
> Mike Kazantsev found 3.5 kernels and beyond were leaking memory,
> and tracked the faulty commit to a1c7fff7e18f59e (net:
> netdev_alloc_skb() use build_skb()
> 
> While this commit seems fine, it uncovered a bug introduced
> in commit bad43ca8325 (net: introduce skb_try_coalesce()), in function
> kfree_skb_partial() :
> 
> If head is stolen, we free the sk_buff,
> without removing references on secpath (skb->sp).
> 
> So IPsec + IP defrag/reassembly (using skb coalescing), or
> TCP coalescing could leak secpath objects.
> 
> Fix this bug by calling skb_release_head_state(skb) to properly
> release all possible references to linked objects.
> 
> Reported-by: Mike Kazantsev <mk.fraggod@gmail.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Bisected-by: Mike Kazantsev <mk.fraggod@gmail.com>
> Tested-by: Mike Kazantsev <mk.fraggod@gmail.com>

Applied and queued up for -stable, thanks!

> It seems TCP stack could immediately release secpath references instead
> of waiting skb are eaten by consumer, thats will be a followup patch.

Indeed.
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Patch

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 6e04b1f..4007c14 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3379,10 +3379,12 @@  EXPORT_SYMBOL(__skb_warn_lro_forwarding);
 
 void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)
 {
-	if (head_stolen)
+	if (head_stolen) {
+		skb_release_head_state(skb);
 		kmem_cache_free(skbuff_head_cache, skb);
-	else
+	} else {
 		__kfree_skb(skb);
+	}
 }
 EXPORT_SYMBOL(kfree_skb_partial);