diff options
Diffstat (limited to 'drivers/net/ppp')
| -rw-r--r-- | drivers/net/ppp/ppp_generic.c | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 815108c98b78..ca77661688c0 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -72,6 +72,17 @@ #define PPP_PROTO_LEN 2 #define PPP_LCP_HDRLEN 4 +/* The filter instructions generated by libpcap are constructed + * assuming a four-byte PPP header on each packet, where the last + * 2 bytes are the protocol field defined in the RFC and the first + * byte of the first 2 bytes indicates the direction. + * The second byte is currently unused, but we still need to initialize + * it to prevent crafted BPF programs from reading them which would + * cause reading of uninitialized data. + */ +#define PPP_FILTER_OUTBOUND_TAG 0x0100 +#define PPP_FILTER_INBOUND_TAG 0x0000 + /* * An instance of /dev/ppp can be associated with either a ppp * interface unit or a ppp channel. In both cases, file->private_data @@ -1765,10 +1776,10 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb) if (proto < 0x8000) { #ifdef CONFIG_PPP_FILTER - /* check if we should pass this packet */ - /* the filter instructions are constructed assuming - a four-byte PPP header on each packet */ - *(u8 *)skb_push(skb, 2) = 1; + /* check if the packet passes the pass and active filters. + * See comment for PPP_FILTER_OUTBOUND_TAG above. + */ + *(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_OUTBOUND_TAG); if (ppp->pass_filter && bpf_prog_run(ppp->pass_filter, skb) == 0) { if (ppp->debug & 1) @@ -2485,14 +2496,13 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb) /* network protocol frame - give it to the kernel */ #ifdef CONFIG_PPP_FILTER - /* check if the packet passes the pass and active filters */ - /* the filter instructions are constructed assuming - a four-byte PPP header on each packet */ if (ppp->pass_filter || ppp->active_filter) { if (skb_unclone(skb, GFP_ATOMIC)) goto err; - - *(u8 *)skb_push(skb, 2) = 0; + /* Check if the packet passes the pass and active filters. + * See comment for PPP_FILTER_INBOUND_TAG above. + */ + *(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG); if (ppp->pass_filter && bpf_prog_run(ppp->pass_filter, skb) == 0) { if (ppp->debug & 1) |