net: hsr: check for return value of skb_put_padto()

skb_put_padto() can fail. So check for return type and return NULL
for skb. Caller checks for skb and acts correctly if it is NULL.

Fixes: 6d6148bc ("net: hsr: fix incorrect lsdu size in the tag of HSR frames for small frames")
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/hsr/hsr_forward.c

@@ -120,15 +120,17 @@ static struct sk_buff *frame_get_stripped_skb(struct hsr_frame_info *frame,
 	return skb_clone(frame->skb_std, GFP_ATOMIC);
 }
 
-static void hsr_fill_tag(struct sk_buff *skb, struct hsr_frame_info *frame,
-			 struct hsr_port *port, u8 proto_version)
+static struct sk_buff *hsr_fill_tag(struct sk_buff *skb,
+				    struct hsr_frame_info *frame,
+				    struct hsr_port *port, u8 proto_version)
 {
 	struct hsr_ethhdr *hsr_ethhdr;
 	int lane_id;
 	int lsdu_size;
 
 	/* pad to minimum packet size which is 60 + 6 (HSR tag) */
-	skb_put_padto(skb, ETH_ZLEN + HSR_HLEN);
+	if (skb_put_padto(skb, ETH_ZLEN + HSR_HLEN))
+		return NULL;
 
 	if (port->type == HSR_PT_SLAVE_A)
 		lane_id = 0;
@@ -147,6 +149,8 @@ static void hsr_fill_tag(struct sk_buff *skb, struct hsr_frame_info *frame,
 	hsr_ethhdr->hsr_tag.encap_proto = hsr_ethhdr->ethhdr.h_proto;
 	hsr_ethhdr->ethhdr.h_proto = htons(proto_version ?
 			ETH_P_HSR : ETH_P_PRP);
+
+	return skb;
 }
 
 static struct sk_buff *create_tagged_skb(struct sk_buff *skb_o,
@@ -175,9 +179,10 @@ static struct sk_buff *create_tagged_skb(struct sk_buff *skb_o,
 	memmove(dst, src, movelen);
 	skb_reset_mac_header(skb);
 
-	hsr_fill_tag(skb, frame, port, port->hsr->prot_version);
-
-	return skb;
+	/* skb_put_padto free skb on error and hsr_fill_tag returns NULL in
+	 * that case
+	 */
+	return hsr_fill_tag(skb, frame, port, port->hsr->prot_version);
 }
 
 /* If the original frame was an HSR tagged frame, just clone it to be sent