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dccp: limit sk_filter trim to payload

Browse source 
Dccp verifies packet integrity, including length, at initial rcv in
dccp_invalid_packet, later pulls headers in dccp_enqueue_skb.

A call to sk_filter in-between can cause __skb_pull to wrap skb->len.
skb_copy_datagram_msg interprets this as a negative value, so
(correctly) fails with EFAULT. The negative length is reported in
ioctl SIOCINQ or possibly in a DCCP_WARN in dccp_close.

Introduce an sk_receive_skb variant that caps how small a filter
program can trim packets, and call this in dccp with the header
length. Excessively trimmed packets are now processed normally and
queued for reception as 0B payloads.

Fixes: 7c657876b6 ("[DCCP]: Initial implementation")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2016-07-12 18:18:57 -04:00 • committed by David S. Miller
parent f4979fcea7
commit 4f0c40d944
4 changed files with 13 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
include/net/sock.h
View file

@ -1576,7 +1576,13 @@ static inline void sock_put(struct sock *sk)
*/
void sock_gen_put(struct sock *sk);
int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested);
int __sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested,
unsigned int trim_cap);
static inline int sk_receive_skb(struct sock *sk, struct sk_buff *skb,
const int nested)
{
return __sk_receive_skb(sk, skb, nested, 1);
}
static inline void sk_tx_queue_set(struct sock *sk, int tx_queue)
{

7
net/core/sock.c
View file

@ -452,11 +452,12 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
}
EXPORT_SYMBOL(sock_queue_rcv_skb);
int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested)
int __sk_receive_skb(struct sock *sk, struct sk_buff *skb,
const int nested, unsigned int trim_cap)
{
int rc = NET_RX_SUCCESS;
if (sk_filter(sk, skb))
if (sk_filter_trim_cap(sk, skb, trim_cap))
goto discard_and_relse;
skb->dev = NULL;
@ -492,7 +493,7 @@ discard_and_relse:
kfree_skb(skb);
goto out;
}
EXPORT_SYMBOL(sk_receive_skb);
EXPORT_SYMBOL(__sk_receive_skb);
struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
{

2
net/dccp/ipv4.c
View file

@ -868,7 +868,7 @@ lookup:
goto discard_and_relse;
nf_reset(skb);
return sk_receive_skb(sk, skb, 1);
return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4);
no_dccp_socket:
if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))

2
net/dccp/ipv6.c
View file

@ -732,7 +732,7 @@ lookup:
if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
goto discard_and_relse;
return sk_receive_skb(sk, skb, 1) ? -1 : 0;
return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4) ? -1 : 0;
no_dccp_socket:
if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))