[PATCH net v1 1/1] net: selftests: initialize TCP header and skb payload with zero

[PATCH net v1 1/1] net: selftests: initialize TCP header and skb payload with zero

[Oleksij Rempel]

Zero-initialize TCP header via memset() to avoid garbage values that
may affect checksum or behavior during test transmission.

Also zero-fill allocated payload and padding regions using memset()
after skb_put(), ensuring deterministic content for all outgoing
test packets.

Fixes: 3e1e58d64c3d ("net: add generic selftest support")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: stable@vger.kernel.org
---
 net/core/selftests.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/net/core/selftests.c b/net/core/selftests.c
index e99ae983fca9..35f807ea9952 100644
--- a/net/core/selftests.c
+++ b/net/core/selftests.c
@@ -100,10 +100,10 @@ static struct sk_buff *net_test_get_skb(struct net_device *ndev,
 	ehdr->h_proto = htons(ETH_P_IP);
 
 	if (attr->tcp) {
+		memset(thdr, 0, sizeof(*thdr));
 		thdr->source = htons(attr->sport);
 		thdr->dest = htons(attr->dport);
 		thdr->doff = sizeof(struct tcphdr) / 4;
-		thdr->check = 0;
 	} else {
 		uhdr->source = htons(attr->sport);
 		uhdr->dest = htons(attr->dport);
@@ -144,10 +144,18 @@ static struct sk_buff *net_test_get_skb(struct net_device *ndev,
 	attr->id = net_test_next_id;
 	shdr->id = net_test_next_id++;
 
-	if (attr->size)
-		skb_put(skb, attr->size);
-	if (attr->max_size && attr->max_size > skb->len)
-		skb_put(skb, attr->max_size - skb->len);
+	if (attr->size) {
+		void *payload = skb_put(skb, attr->size);
+
+		memset(payload, 0, attr->size);
+	}
+
+	if (attr->max_size && attr->max_size > skb->len) {
+		size_t pad_len = attr->max_size - skb->len;
+		void *pad = skb_put(skb, pad_len);
+
+		memset(pad, 0, pad_len);
+	}
 
 	skb->csum = 0;
 	skb->ip_summed = CHECKSUM_PARTIAL;
-- 
2.39.5

Re: [PATCH net v1 1/1] net: selftests: initialize TCP header and skb payload with zero

[Simon Horman]

On Wed, Apr 16, 2025 at 06:01:25PM +0200, Oleksij Rempel wrote:
> Zero-initialize TCP header via memset() to avoid garbage values that
> may affect checksum or behavior during test transmission.
> 
> Also zero-fill allocated payload and padding regions using memset()
> after skb_put(), ensuring deterministic content for all outgoing
> test packets.
> 
> Fixes: 3e1e58d64c3d ("net: add generic selftest support")
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> Cc: stable@vger.kernel.org

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net v1 1/1] net: selftests: initialize TCP header and skb payload with zero

[Jakub Kicinski]

On Wed, 16 Apr 2025 18:01:25 +0200 Oleksij Rempel wrote:
> Zero-initialize TCP header via memset() to avoid garbage values that
> may affect checksum or behavior during test transmission.
> 
> Also zero-fill allocated payload and padding regions using memset()
> after skb_put(), ensuring deterministic content for all outgoing
> test packets.

This has been applied, thanks!

patchwork-but is down, it seems, and it's out of our control :(