[PATCH next] net/core/dev: Warn on an impossibly short offload frame

When signaling that a GRO frame is ready to be processed, the network stack
correctly checks length and aborts processing when a frame is less than 14
bytes. However, such a condition is really indicative of a broken driver,
and should be loudly signaled, rather than silently dropped as the case is
today.

Convert the condition to use WARN_ON() to ensure that the stack loudly
complains about such broken drivers.

Signed-off-by: Aaron Conole <redacted>
---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 914b4a2..8af4e29 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -4579,7 +4579,7 @@ static struct sk_buff *napi_frags_skb(struct napi_struct *napi)
 	eth = skb_gro_header_fast(skb, 0);
 	if (unlikely(skb_gro_header_hard(skb, hlen))) {
 		eth = skb_gro_header_slow(skb, hlen, 0);
-		if (unlikely(!eth)) {
+		if (WARN_ON(!eth)) {
 			napi_reuse_skb(napi, skb);
 			return NULL;
 		}

-- 
2.6.4

On Sat, 2016-01-02 at 19:25 -0500, Aaron Conole wrote:

When signaling that a GRO frame is ready to be processed, the network stack
correctly checks length and aborts processing when a frame is less than 14
bytes. However, such a condition is really indicative of a broken driver,
and should be loudly signaled, rather than silently dropped as the case is
today.

Convert the condition to use WARN_ON() to ensure that the stack loudly
complains about such broken drivers.

[]

[]

It's generally a good idea to use
WARN_ON_RATELIMIT or WARN_ON_ONCE.

Joe Perches [off-list ref] writes:

On Sat, 2016-01-02 at 19:25 -0500, Aaron Conole wrote:

quoted

When signaling that a GRO frame is ready to be processed, the network stack
correctly checks length and aborts processing when a frame is less than 14
bytes. However, such a condition is really indicative of a broken driver,
and should be loudly signaled, rather than silently dropped as the case is
today.

Convert the condition to use WARN_ON() to ensure that the stack loudly
complains about such broken drivers.

[]

quoted

diff --git a/net/core/dev.c b/net/core/dev.c

[]

quoted

@@ -4579,7 +4579,7 @@ static struct sk_buff *napi_frags_skb(struct

napi_struct *napi)
 	eth = skb_gro_header_fast(skb, 0);
 	if (unlikely(skb_gro_header_hard(skb, hlen))) {
 		eth = skb_gro_header_slow(skb, hlen, 0);
-		if (unlikely(!eth)) {
+		if (WARN_ON(!eth)) {
 			napi_reuse_skb(napi, skb);
 			return NULL;
 		}

It's generally a good idea to use
WARN_ON_RATELIMIT or WARN_ON_ONCE.

Okay, I'll respin switching to WARN_ON_RATELIMIT, if that's a better
approach.

Thanks for the review, Joe!