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Merge branch 'net-af_packet-be-careful-when-expanding-mac-header-size'

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Eric Dumazet says:

====================
net: af_packet: be careful when expanding mac header size

A recent regression in af_packet needed a preliminary debug patch,
which will presumably be useful for next bugs hunting.

The af_packet fix is to make sure MAC headers are contained in
skb linear part, as GSO stack requests.

v2: CONFIG_DEBUG_NET depends on CONFIG_NET to avoid compile
   errors found by kernel bots.
====================

Link: https://lore.kernel.org/r/20220602161859.2546399-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2022-06-02 10:15:07 -07:00
commit 638696efc1
3 changed files with 13 additions and 4 deletions
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9
include/linux/skbuff.h
View File

@ -2696,7 +2696,14 @@ void *skb_pull(struct sk_buff *skb, unsigned int len);
static inline void *__skb_pull(struct sk_buff *skb, unsigned int len) static inline void *__skb_pull(struct sk_buff *skb, unsigned int len)
{ {
skb->len -= len; skb->len -= len;
BUG_ON(skb->len < skb->data_len); if (unlikely(skb->len < skb->data_len)) {
#if defined(CONFIG_DEBUG_NET)
skb->len += len;
pr_err("__skb_pull(len=%u)\n", len);
skb_dump(KERN_ERR, skb, false);
#endif
BUG();
}
return skb->data += len; return skb->data += len;
} }

2
net/Kconfig.debug
View File

@ -20,7 +20,7 @@ config NET_NS_REFCNT_TRACKER
config DEBUG_NET config DEBUG_NET
bool "Add generic networking debug" bool "Add generic networking debug"
depends on DEBUG_KERNEL depends on DEBUG_KERNEL && NET
help help
Enable extra sanity checks in networking. Enable extra sanity checks in networking.
This is mostly used by fuzzers, but is safe to select. This is mostly used by fuzzers, but is safe to select.

6
net/packet/af_packet.c
View File

@ -1935,8 +1935,10 @@ static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
/* Move network header to the right position for VLAN tagged packets */ /* Move network header to the right position for VLAN tagged packets */
if (likely(skb->dev->type == ARPHRD_ETHER) && if (likely(skb->dev->type == ARPHRD_ETHER) &&
eth_type_vlan(skb->protocol) && eth_type_vlan(skb->protocol) &&
__vlan_get_protocol(skb, skb->protocol, &depth) != 0) __vlan_get_protocol(skb, skb->protocol, &depth) != 0) {
skb_set_network_header(skb, depth); if (pskb_may_pull(skb, depth))
skb_set_network_header(skb, depth);
}
skb_probe_transport_header(skb); skb_probe_transport_header(skb);
} }