Commit cfe77022 authored by David Dull's avatar David Dull Committed by Florian Westphal
Browse files

netfilter: x_tables: guard option walkers against 1-byte tail reads 



When the last byte of options is a non-single-byte option kind, walkers
that advance with i += op[i + 1] ? : 1 can read op[i + 1] past the end
of the option area.

Add an explicit i == optlen - 1 check before dereferencing op[i + 1]
in xt_tcpudp and xt_dccp option walkers.

Fixes: 2e4e6a17 ("[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables")
Signed-off-by: default avatarDavid Dull <monderasdor@gmail.com>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
parent d6d8cd2d

net/netfilter/xt_dccp.c

+2 −2
Original line number Diff line number Diff line
@@ -62,7 +62,7 @@ dccp_find_option(u_int8_t option, 
			return true;

		}



		if (op[i] < 2)

		if (op[i] < 2 || i == optlen - 1)

			i++;

		else

			i += op[i + 1] ? : 1;

net/netfilter/xt_tcpudp.c

+4 −2
Original line number Diff line number Diff line
@@ -59,8 +59,10 @@ tcp_find_option(u_int8_t option, 


	for (i = 0; i < optlen; ) {

		if (op[i] == option) return !invert;

		if (op[i] < 2) i++;

		else i += op[i+1]?:1;

		if (op[i] < 2 || i == optlen - 1)

			i++;

		else

			i += op[i + 1] ? : 1;

	}



	return invert;