[ 157/173] ipv4: ip_check_defrag must not modify skb before unsharing
From: Ben Hutchings <hidden>
Date: 2012-12-28 19:54:35
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lkml
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johannes Berg <redacted> [ Upstream commit 1bf3751ec90cc3174e01f0d701e8449ce163d113 ] ip_check_defrag() might be called from af_packet within the RX path where shared SKBs are used, so it must not modify the input SKB before it has unshared it for defragmentation. Use skb_copy_bits() to get the IP header and only pull in everything later. The same is true for the other caller in macvlan as it is called from dev->rx_handler which can also get a shared SKB. Reported-by: Eric Leblond <redacted> Signed-off-by: Johannes Berg <redacted> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <redacted> --- net/ipv4/ip_fragment.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index fdaabf2..a4e7131 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c@@ -684,28 +684,27 @@ EXPORT_SYMBOL(ip_defrag); struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user) { - const struct iphdr *iph; + struct iphdr iph; u32 len; if (skb->protocol != htons(ETH_P_IP)) return skb; - if (!pskb_may_pull(skb, sizeof(struct iphdr))) + if (!skb_copy_bits(skb, 0, &iph, sizeof(iph))) return skb; - iph = ip_hdr(skb); - if (iph->ihl < 5 || iph->version != 4) + if (iph.ihl < 5 || iph.version != 4) return skb; - if (!pskb_may_pull(skb, iph->ihl*4)) - return skb; - iph = ip_hdr(skb); - len = ntohs(iph->tot_len); - if (skb->len < len || len < (iph->ihl * 4)) + + len = ntohs(iph.tot_len); + if (skb->len < len || len < (iph.ihl * 4)) return skb; - if (ip_is_fragment(ip_hdr(skb))) { + if (ip_is_fragment(&iph)) { skb = skb_share_check(skb, GFP_ATOMIC); if (skb) { + if (!pskb_may_pull(skb, iph.ihl*4)) + return skb; if (pskb_trim_rcsum(skb, len)) return skb; memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));