Message ID | 1491242111.10124.32.camel@edumazet-glaptop3.roam.corp.google.com |
---|---|
State | Accepted |
Delegated to: | Pablo Neira |
Headers | show |
On Mon, Apr 03, 2017 at 10:55:11AM -0700, Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > Denys provided an awesome KASAN report pointing to an use > after free in xt_TCPMSS > > I have provided three patches to fix this issue, either in xt_TCPMSS or > in xt_tcpudp.c. It seems xt_TCPMSS patch has the smallest possible > impact. Applied to nf.git, thanks! -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2017-04-08 23:24, Pablo Neira Ayuso wrote: > On Mon, Apr 03, 2017 at 10:55:11AM -0700, Eric Dumazet wrote: >> From: Eric Dumazet <edumazet@google.com> >> >> Denys provided an awesome KASAN report pointing to an use >> after free in xt_TCPMSS >> >> I have provided three patches to fix this issue, either in xt_TCPMSS >> or >> in xt_tcpudp.c. It seems xt_TCPMSS patch has the smallest possible >> impact. > > Applied to nf.git, thanks! Any plans to queue it to stable trees? It seems affected kernel for years. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c index 27241a767f17b4b27d24095a31e5e9a2d3e29ce4..c64aca611ac5c5f81ad7c925652bbb90554763ac 100644 --- a/net/netfilter/xt_TCPMSS.c +++ b/net/netfilter/xt_TCPMSS.c @@ -104,7 +104,7 @@ tcpmss_mangle_packet(struct sk_buff *skb, tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); tcp_hdrlen = tcph->doff * 4; - if (len < tcp_hdrlen) + if (len < tcp_hdrlen || tcp_hdrlen < sizeof(struct tcphdr)) return -1; if (info->mss == XT_TCPMSS_CLAMP_PMTU) { @@ -152,6 +152,10 @@ tcpmss_mangle_packet(struct sk_buff *skb, if (len > tcp_hdrlen) return 0; + /* tcph->doff has 4 bits, do not wrap it to 0 */ + if (tcp_hdrlen >= 15 * 4) + return 0; + /* * MSS Option not found ?! add it.. */