[PATCH] net: fix secpath kmemleak

From: Eric Dumazet <redacted>

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 <redacted>
Signed-off-by: Eric Dumazet <redacted>
Bisected-by: Mike Kazantsev [off-list ref]
Tested-by: Mike Kazantsev <redacted>
---
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(-)

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);
 



--

To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>