Merge branch 'inet-prevent-skb-changes-in-udp-4-6-_lib_lookup_skb'

Eric Dumazet says:

====================
inet: prevent skb changes in udp{4|6}_lib_lookup_skb()

This came while reviewing Alexander Lobakin patch against UDP GRO:

We want to make sure skb wont be changed by these helpers
while it is owned by GRO stack.
====================

Link: https://lore.kernel.org/r/20201109231349.20946-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/ip.h

@@ -99,7 +99,7 @@ static inline void ipcm_init_sk(struct ipcm_cookie *ipcm,
 #define PKTINFO_SKB_CB(skb) ((struct in_pktinfo *)((skb)->cb))
 
 /* return enslaved device index if relevant */
-static inline int inet_sdif(struct sk_buff *skb)
+static inline int inet_sdif(const struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
 	if (skb && ipv4_l3mdev_skb(IPCB(skb)->flags))

include/net/udp.h

@@ -164,7 +164,7 @@ static inline void udp_csum_pull_header(struct sk_buff *skb)
 	UDP_SKB_CB(skb)->cscov -= sizeof(struct udphdr);
 }
 
-typedef struct sock *(*udp_lookup_t)(struct sk_buff *skb, __be16 sport,
+typedef struct sock *(*udp_lookup_t)(const struct sk_buff *skb, __be16 sport,
 				     __be16 dport);
 
 INDIRECT_CALLABLE_DECLARE(struct sk_buff *udp4_gro_receive(struct list_head *,
@@ -313,7 +313,7 @@ struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
 			       __be32 daddr, __be16 dport, int dif, int sdif,
 			       struct udp_table *tbl, struct sk_buff *skb);
-struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
 struct sock *udp6_lib_lookup(struct net *net,
 			     const struct in6_addr *saddr, __be16 sport,
@@ -324,7 +324,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
 			       const struct in6_addr *daddr, __be16 dport,
 			       int dif, int sdif, struct udp_table *tbl,
 			       struct sk_buff *skb);
-struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
 
 /* UDP uses skb->dev_scratch to cache as much information as possible and avoid

net/ipv4/udp.c

@@ -541,7 +541,7 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
 				 inet_sdif(skb), udptable, skb);
 }
 
-struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport)
 {
 	const struct iphdr *iph = ip_hdr(skb);

net/ipv6/udp.c

@@ -276,7 +276,7 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
 				 inet6_sdif(skb), udptable, skb);
 }
 
-struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
+struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport)
 {
 	const struct ipv6hdr *iph = ipv6_hdr(skb);