net: psample: fix flag being set in wrong skb

A typo makes PSAMPLE_ATTR_SAMPLE_RATE netlink flag be added to the wrong
sk_buff.

Fix the error and make the input sk_buff pointer "const" so that it
doesn't happen again.
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Fixes: 7b1b2b60 ("net: psample: allow using rate as probability")
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://patch.msgid.link/20240710171004.2164034-1-amorenoz@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/psample.h

@@ -38,13 +38,15 @@ struct sk_buff;
 
 #if IS_ENABLED(CONFIG_PSAMPLE)
 
-void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
-			   u32 sample_rate, const struct psample_metadata *md);
+void psample_sample_packet(struct psample_group *group,
+			   const struct sk_buff *skb, u32 sample_rate,
+			   const struct psample_metadata *md);
 
 #else
 
 static inline void psample_sample_packet(struct psample_group *group,
-					 struct sk_buff *skb, u32 sample_rate,
+					 const struct sk_buff *skb,
+					 u32 sample_rate,
 					 const struct psample_metadata *md)
 {
 }

net/psample/psample.c

@@ -360,8 +360,9 @@ static int psample_tunnel_meta_len(struct ip_tunnel_info *tun_info)
 }
 #endif
 
-void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
-			   u32 sample_rate, const struct psample_metadata *md)
+void psample_sample_packet(struct psample_group *group,
+			   const struct sk_buff *skb, u32 sample_rate,
+			   const struct psample_metadata *md)
 {
 	ktime_t tstamp = ktime_get_real();
 	int out_ifindex = md->out_ifindex;
@@ -498,7 +499,7 @@ void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
 		goto error;
 
 	if (md->rate_as_probability)
-		nla_put_flag(skb, PSAMPLE_ATTR_SAMPLE_PROBABILITY);
+		nla_put_flag(nl_skb, PSAMPLE_ATTR_SAMPLE_PROBABILITY);
 
 	genlmsg_end(nl_skb, data);
 	genlmsg_multicast_netns(&psample_nl_family, group->net, nl_skb, 0,