netfilter: nf_conntrack_dccp: fix skb_header_pointer API usages
Some occurences in the netfilter tree use skb_header_pointer() in
the following way ...
struct dccp_hdr _dh, *dh;
...
skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
... where dh itself is a pointer that is being passed as the copy
buffer. Instead, we need to use &_dh as the forth argument so that
we're copying the data into an actual buffer that sits on the stack.
Currently, we probably could overwrite memory on the stack (e.g.
with a possibly mal-formed DCCP packet), but unintentionally, as
we only want the buffer to be placed into _dh variable.
Fixes: 2bc780499aa3 ("[NETFILTER]: nf_conntrack: add DCCP protocol support")
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_conntrack_proto_dccp.c b/net/netfilter/nf_conntrack_proto_dccp.c
index 24fdce2..31dbf00 100644
--- a/net/netfilter/nf_conntrack_proto_dccp.c
+++ b/net/netfilter/nf_conntrack_proto_dccp.c
@@ -431,7 +431,7 @@
const char *msg;
u_int8_t state;
- dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
+ dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &_dh);
BUG_ON(dh == NULL);
state = dccp_state_table[CT_DCCP_ROLE_CLIENT][dh->dccph_type][CT_DCCP_NONE];
@@ -488,7 +488,7 @@
u_int8_t type, old_state, new_state;
enum ct_dccp_roles role;
- dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
+ dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &_dh);
BUG_ON(dh == NULL);
type = dh->dccph_type;
@@ -579,7 +579,7 @@
unsigned int cscov;
const char *msg;
- dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
+ dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &_dh);
if (dh == NULL) {
msg = "nf_ct_dccp: short packet ";
goto out_invalid;