diff options
| author | Pablo Neira Ayuso <pablo@netfilter.org> | 2013-07-25 10:46:46 +0200 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2013-08-01 11:45:15 +0200 |
| commit | a206bcb3b02025b23137f3228109d72e0f835c05 (patch) | |
| tree | 517502da0639006d869a3d407d78132c5acb3dea /net/netfilter/xt_TCPOPTSTRIP.c | |
| parent | 71ffe9c77dd7a2b62207953091efa8dafec958dd (diff) | |
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/netfilter/xt_TCPOPTSTRIP.c')
| -rw-r--r-- | net/netfilter/xt_TCPOPTSTRIP.c | 10 |
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])) |