lkml.org 
[lkml]   [2023]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()
Date
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
\
 
 \ /
  Last update: 2023-12-02 17:15    [W:0.088 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site