Merge branch 'net-add-debug-checks-to-skb_reset_xxx_header'

Eric Dumazet says:

====================
net: add debug checks to skb_reset_xxx_header()

Add debug checks (only enabled for CONFIG_DEBUG_NET=y builds),
to catch bugs earlier.
====================

Link: https://patch.msgid.link/20241105174403.850330-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 35 insertions, 12 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 48f1e0fa2a13..e5095d75abba 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2909,9 +2909,19 @@ static inline void skb_reset_inner_headers(struct sk_buff *skb)
 	skb->inner_transport_header = skb->transport_header;
 }
 
+static inline int skb_mac_header_was_set(const struct sk_buff *skb)
+{
+	return skb->mac_header != (typeof(skb->mac_header))~0U;
+}
+
 static inline void skb_reset_mac_len(struct sk_buff *skb)
 {
-	skb->mac_len = skb->network_header - skb->mac_header;
+	if (!skb_mac_header_was_set(skb)) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		skb->mac_len = 0;
+	} else {
+		skb->mac_len = skb->network_header - skb->mac_header;
+	}
 }
 
 static inline unsigned char *skb_inner_transport_header(const struct sk_buff
@@ -2927,7 +2937,10 @@ static inline int skb_inner_transport_offset(const struct sk_buff *skb)
 
 static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
 {
-	skb->inner_transport_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->inner_transport_header))offset);
+	skb->inner_transport_header = offset;
 }
 
 static inline void skb_set_inner_transport_header(struct sk_buff *skb,
@@ -2944,7 +2957,10 @@ static inline unsigned char *skb_inner_network_header(const struct sk_buff *skb)
 
 static inline void skb_reset_inner_network_header(struct sk_buff *skb)
 {
-	skb->inner_network_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->inner_network_header))offset);
+	skb->inner_network_header = offset;
 }
 
 static inline void skb_set_inner_network_header(struct sk_buff *skb,
@@ -2966,7 +2982,10 @@ static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
 
 static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
 {
-	skb->inner_mac_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->inner_mac_header))offset);
+	skb->inner_mac_header = offset;
 }
 
 static inline void skb_set_inner_mac_header(struct sk_buff *skb,
@@ -2988,7 +3007,10 @@ static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 
 static inline void skb_reset_transport_header(struct sk_buff *skb)
 {
-	skb->transport_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->transport_header))offset);
+	skb->transport_header = offset;
 }
 
 static inline void skb_set_transport_header(struct sk_buff *skb,
@@ -3005,7 +3027,10 @@ static inline unsigned char *skb_network_header(const struct sk_buff *skb)
 
 static inline void skb_reset_network_header(struct sk_buff *skb)
 {
-	skb->network_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->network_header))offset);
+	skb->network_header = offset;
 }
 
 static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
@@ -3014,11 +3039,6 @@ static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
 	skb->network_header += offset;
 }
 
-static inline int skb_mac_header_was_set(const struct sk_buff *skb)
-{
-	return skb->mac_header != (typeof(skb->mac_header))~0U;
-}
-
 static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
 {
 	DEBUG_NET_WARN_ON_ONCE(!skb_mac_header_was_set(skb));
@@ -3043,7 +3063,10 @@ static inline void skb_unset_mac_header(struct sk_buff *skb)
 
 static inline void skb_reset_mac_header(struct sk_buff *skb)
 {
-	skb->mac_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->mac_header))offset);
+	skb->mac_header = offset;
 }
 
 static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)