netlink: Avoid netlink mmap alloc if msg size exceeds frame size
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>
Signed-off-by: Jesse Gross <jesse@nicira.com>
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 @@
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 @@
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;