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net: Add skb_dst_check_unset

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To prevent dst_entry leaks, add warning when the non-NULL dst_entry
is rewritten.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250818154032.3173645-8-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Stanislav Fomichev
2025-08-18 08:40:32 -07:00
committed by Jakub Kicinski
parent 3e31075a11
commit a890348adc
1 changed files with 9 additions and 0 deletions
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9
include/linux/skbuff.h
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@@ -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;