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| author | Eric Dumazet <edumazet@google.com> | 2012-12-20 16:00:27 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-12-21 13:14:01 -0800 |
| commit | f7e75ba1772bc712af0070655ffd8b09906993b5 (patch) | |
| tree | ef32b318efe584f845f05eb7f65daca803abb6a1 /net/ipv4/ip_gre.c | |
| parent | 412ed94744d16806fbec3bd250fd94e71cde5a1f (diff) | |
| download | linux-f7e75ba1772bc712af0070655ffd8b09906993b5.tar.gz | |
ip_gre: fix possible use after free
Once skb_realloc_headroom() is called, tiph might point to freed memory. Cache tiph->ttl value before the reallocation, to avoid unexpected behavior. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Isaku Yamahata <yamahata@valinux.co.jp> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_gre.c')
| -rw-r--r-- | net/ipv4/ip_gre.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 8fcf0ed76548..58cb627560dd 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -750,6 +750,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev int gre_hlen; __be32 dst; int mtu; + u8 ttl; if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb)) @@ -815,6 +816,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev goto tx_error; } + ttl = tiph->ttl; tos = tiph->tos; if (tos == 1) { tos = 0; @@ -907,6 +909,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev dev_kfree_skb(skb); skb = new_skb; old_iph = ip_hdr(skb); + /* Warning : tiph value might point to freed memory */ } skb_reset_transport_header(skb); @@ -930,8 +933,9 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev iph->tos = ipgre_ecn_encapsulate(tos, old_iph, skb); iph->daddr = fl4.daddr; iph->saddr = fl4.saddr; + iph->ttl = ttl; - if ((iph->ttl = tiph->ttl) == 0) { + if (ttl == 0) { if (skb->protocol == htons(ETH_P_IP)) iph->ttl = old_iph->ttl; #if IS_ENABLED(CONFIG_IPV6) |