mptcp: Fix out of bounds when parsing TCP options

[ Upstream commit 07718be265680dcf496347d475ce1a5442f55ad7 ]

The TCP option parser in mptcp (mptcp_get_options) could read one byte
out of bounds. When the length is 1, the execution flow gets into the
loop, reads one byte of the opcode, and if the opcode is neither
TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds the
length of 1.

This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack
out of bounds when parsing TCP options.").

Cc: Young Xiao <92siuyang@gmail.com>
Fixes: cec37a6e41aa ("mptcp: Handle MP_CAPABLE options for outgoing connections")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 91034a221983c4cd586df13cee2b89a2b5019d5f..ac0233c9cd349ff7425bdba4c9854c1f1048cff0 100644 (file)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -314,6 +314,8 @@ void mptcp_get_options(const struct sk_buff *skb,
                        length--;
                        continue;
                default:
+                       if (length < 2)
+                               return;
                        opsize = *ptr++;
                        if (opsize < 2) /* "silly options" */
                                return;