net: test tailroom before appending to linear skb

Device features may change during transmission. In particular with corking, a device may toggle scatter-gather in between allocating and writing to an skb. Do not unconditionally assume that !NETIF_F_SG at write time implies that the same held at alloc time and thus the skb has sufficient tailroom. This issue predates git history. Fixes: 1da177e ("Linux-2.6.12-rc2") Reported-by: Eric Dumazet <[email protected]> Signed-off-by: Willem de Bruijn <[email protected]> Reviewed-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
olifre · May 17, 2018 · 113f99c · 113f99c
1 parent 374edea
commit 113f99c
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
@@ -1045,7 +1045,8 @@ static int __ip_append_data(struct sock *sk,
 		if (copy > length)
 			copy = length;
 
-		if (!(rt->dst.dev->features&NETIF_F_SG)) {
+		if (!(rt->dst.dev->features&NETIF_F_SG) &&
+		    skb_tailroom(skb) >= copy) {
 			unsigned int off;
 
 			off = skb->len;

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
@@ -1503,7 +1503,8 @@ static int __ip6_append_data(struct sock *sk,
 		if (copy > length)
 			copy = length;
 
-		if (!(rt->dst.dev->features&NETIF_F_SG)) {
+		if (!(rt->dst.dev->features&NETIF_F_SG) &&
+		    skb_tailroom(skb) >= copy) {
 			unsigned int off;
 
 			off = skb->len;