dccp: handle invalid feature options length

A length of zero (after subtracting two for the type and len fields) for
the DCCPO_{CHANGE,CONFIRM}_{L,R} options will cause an underflow due to
the subtraction.  The subsequent code may read past the end of the
options value buffer when parsing.  I'm unsure of what the consequences
of this might be, but it's probably not good.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: stable@kernel.org
Acked-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dccp/options.c b/net/dccp/options.c
index f06ffcfc8d712421040c71a56513b90dcfca96c7..4b2ab657ac8e616f415312d96a2b9c0189489a18 100644 (file)
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -123,6 +123,8 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
                case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
                        if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
                                break;
+                       if (len == 0)
+                               goto out_invalid_option;
                        rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
                                                    *value, value + 1, len - 1);
                        if (rc)