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ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()

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In ipgre_xmit(), skb_pull() may fail even if pskb_inet_may_pull() returns
true. For example, applications can use PF_PACKET to create a malformed
packet with no IP header. This type of packet causes a problem such as
uninit-value access.

This patch ensures that skb_pull() can pull the required size by checking
the skb with pskb_network_may_pull() before skb_pull().

Fixes: c544193214 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Suman Ghosh <sumang@marvell.com>
Link: https://lore.kernel.org/r/20231202161441.221135-1-syoshida@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Shigeru Yoshida 2023-12-03 01:14:41 +09:00 committed by Paolo Abeni
parent efd563ff1a
commit 80d875cfc9
1 changed files with 7 additions and 4 deletions
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11
net/ipv4/ip_gre.c
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@ -635,15 +635,18 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
}
if (dev->header_ops) {
int pull_len = tunnel->hlen + sizeof(struct iphdr);
if (skb_cow_head(skb, 0))
goto free_skb;
tnl_params = (const struct iphdr *)skb->data;
/* Pull skb since ip_tunnel_xmit() needs skb->data pointing
* to gre header.
*/
skb_pull(skb, tunnel->hlen + sizeof(struct iphdr));
if (!pskb_network_may_pull(skb, pull_len))
goto free_skb;
/* ip_tunnel_xmit() needs skb->data pointing to gre header. */
skb_pull(skb, pull_len);
skb_reset_mac_header(skb);
if (skb->ip_summed == CHECKSUM_PARTIAL &&