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[net-next,2/7] netlink: Avoid netlink mmap alloc if msg size exceeds frame size

Message ID 6eaae5950aa4356aac968da357f95f097fcf561f.1385813891.git.tgraf@suug.ch
State Awaiting Upstream, archived
Delegated to: David Miller
Headers show

Commit Message

Thomas Graf Nov. 30, 2013, 12:21 p.m. UTC 
An insufficent ring frame size configuration can lead to an
unnecessary skb allocation for every Netlink message. Check frame
size before taking the queue lock and allocating the skb and
re-check with lock to be safe.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
---
 net/netlink/af_netlink.c | 4 ++++
 1 file changed, 4 insertions(+)
diff mbox

Patch

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index bca50b9..6433489 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1769,6 +1769,9 @@  struct sk_buff *netlink_alloc_skb(struct sock *ssk, unsigned int size,
 	if (ring->pg_vec == NULL)
 		goto out_put;
 
+	if (ring->frame_size - NL_MMAP_HDRLEN < size)
+		goto out_put;
+
 	skb = alloc_skb_head(gfp_mask);
 	if (skb == NULL)
 		goto err1;
@@ -1778,6 +1781,7 @@  struct sk_buff *netlink_alloc_skb(struct sock *ssk, unsigned int size,
 	if (ring->pg_vec == NULL)
 		goto out_free;
 
+	/* check again under lock */
 	maxlen = ring->frame_size - NL_MMAP_HDRLEN;
 	if (maxlen < size)
 		goto out_free;