Messages in this thread Patch in this message | | | From | Shigeru Yoshida <> | Subject | [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit() | Date | Sun, 3 Dec 2023 01:14:41 +0900 |
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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: c54419321455 ("GRE: Refactor GRE tunneling code.") Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> --- v1 -> v2: - Change the title - Update the code with Eric's suggestion https://lore.kernel.org/all/20231126151652.372783-1-syoshida@redhat.com/ --- net/ipv4/ip_gre.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 22a26d1d29a0..5169c3c72cff 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -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 && -- 2.41.0
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