[PATCH net-next v2 7/7] net: Add skb_dst_check_unset
From: Stanislav Fomichev <sdf@fomichev.me>
Date: 2025-08-18 15:40:40
Also in:
linux-staging, lkml, netfilter-devel
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
To prevent dst_entry leaks, add warning when the non-NULL dst_entry is rewritten. Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> --- include/linux/skbuff.h | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 7538ca507ee9..ca8be45dd8be 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h@@ -1159,6 +1159,12 @@ static inline struct dst_entry *skb_dst(const struct sk_buff *skb) return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK); } +static inline void skb_dst_check_unset(struct sk_buff *skb) +{ + DEBUG_NET_WARN_ON_ONCE((skb->_skb_refdst & SKB_DST_PTRMASK) && + !(skb->_skb_refdst & SKB_DST_NOREF)); +} + /** * skb_dstref_steal() - return current dst_entry value and clear it * @skb: buffer
@@ -1188,6 +1194,7 @@ static inline unsigned long skb_dstref_steal(struct sk_buff *skb) */ static inline void skb_dstref_restore(struct sk_buff *skb, unsigned long refdst) { + skb_dst_check_unset(skb); skb->_skb_refdst = refdst; }
@@ -1201,6 +1208,7 @@ static inline void skb_dstref_restore(struct sk_buff *skb, unsigned long refdst) */ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst) { + skb_dst_check_unset(skb); skb->slow_gro |= !!dst; skb->_skb_refdst = (unsigned long)dst; }
@@ -1217,6 +1225,7 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst) */ static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst) { + skb_dst_check_unset(skb); WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); skb->slow_gro |= !!dst; skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
--
2.50.1