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net: warn if mac header was not set
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Make sure skb_mac_header(), skb_mac_offset() and skb_mac_header_len() uses
are not fooled if the mac header has not been set.

These checks are enabled if CONFIG_DEBUG_NET=y

This commit will likely expose existing bugs in linux networking stacks.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220620093017.3366713-1-eric.dumazet@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Eric Dumazet authored and Paolo Abeni committed Jun 21, 2022
1 parent 4336487 commit f9aefd6
Showing 1 changed file with 7 additions and 5 deletions.
12 changes: 7 additions & 5 deletions include/linux/skbuff.h
Original file line number Diff line number Diff line change
Expand Up @@ -2763,8 +2763,14 @@ 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));
return skb->head + skb->mac_header;
}

Expand All @@ -2775,14 +2781,10 @@ static inline int skb_mac_offset(const struct sk_buff *skb)

static inline u32 skb_mac_header_len(const struct sk_buff *skb)
{
DEBUG_NET_WARN_ON_ONCE(!skb_mac_header_was_set(skb));
return skb->network_header - skb->mac_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_unset_mac_header(struct sk_buff *skb)
{
skb->mac_header = (typeof(skb->mac_header))~0U;
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