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authorPablo Neira Ayuso <pablo@netfilter.org>2013-07-25 10:46:46 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2013-08-01 11:45:15 +0200
commita206bcb3b02025b23137f3228109d72e0f835c05 (patch)
tree517502da0639006d869a3d407d78132c5acb3dea /net
parent71ffe9c77dd7a2b62207953091efa8dafec958dd (diff)
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netfilter: xt_TCPOPTSTRIP: fix possible off by one access
Fix a possible off by one access since optlen() touches opt[offset+1] unsafely when i == tcp_hdrlen(skb) - 1. This patch replaces tcp_hdrlen() by the local variable tcp_hdrlen that stores the TCP header length, to save some cycles. Reported-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/xt_TCPOPTSTRIP.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c
index b68fa191710f..625fa1d636a0 100644
--- a/net/netfilter/xt_TCPOPTSTRIP.c
+++ b/net/netfilter/xt_TCPOPTSTRIP.c
@@ -38,7 +38,7 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
struct tcphdr *tcph;
u_int16_t n, o;
u_int8_t *opt;
- int len;
+ int len, tcp_hdrlen;
/* This is a fragment, no TCP header is available */
if (par->fragoff != 0)
@@ -52,7 +52,9 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
return NF_DROP;
tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
- if (tcph->doff * 4 > len)
+ tcp_hdrlen = tcph->doff * 4;
+
+ if (len < tcp_hdrlen)
return NF_DROP;
opt = (u_int8_t *)tcph;
@@ -61,10 +63,10 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
* Walk through all TCP options - if we find some option to remove,
* set all octets to %TCPOPT_NOP and adjust checksum.
*/
- for (i = sizeof(struct tcphdr); i < tcp_hdrlen(skb); i += optl) {
+ for (i = sizeof(struct tcphdr); i < tcp_hdrlen - 1; i += optl) {
optl = optlen(opt, i);
- if (i + optl > tcp_hdrlen(skb))
+ if (i + optl > tcp_hdrlen)
break;
if (!tcpoptstrip_test_bit(info->strip_bmap, opt[i]))