On Mon, Feb 25, 2008 at 08:14:39AM -0800, Jim Westfall wrote:
> Hi
>
> In testing its not safe to trust the payload length we are given in a
> received llc test command header. Instead we should calculate this
> ourselves or run the risk of an skb_over_panic() if the received length in
> the header is > then the actual payload size.
Shouldn't it be discarded?
>
> Signed-off-by: Jim Westfall <[EMAIL PROTECTED]>
>
> diff -urp linux-2.6.24.2.org/include/net/llc_pdu.h
> linux-2.6.24.2/include/net/llc_pdu.h
> --- linux-2.6.24.2.org/include/net/llc_pdu.h 2008-02-10 21:51:11.000000000
> -0800
> +++ linux-2.6.24.2/include/net/llc_pdu.h 2008-02-24 10:23:02.000000000
> -0800
> @@ -348,7 +348,7 @@ static inline void llc_pdu_init_as_test_
> struct llc_pdu_un *ev_pdu = llc_pdu_un_hdr(ev_skb);
> int dsize;
>
> - dsize = ntohs(eth_hdr(ev_skb)->h_proto) - 3;
> + dsize = (ev_skb->tail - (u8 *)ev_pdu) - 3;
In addition, dsize can be a minus. (with & without your patch)
> memcpy(((u8 *)pdu) + 3, ((u8 *)ev_pdu) + 3, dsize);
> skb_put(skb, dsize);
> }
>
> ----- End forwarded message -----
[PATCH] LLC: discard malfromed llc packet
Discard llc packet which has invalid data size.
Signed-off-by: Joonwoo Park <[EMAIL PROTECTED]>
---
net/llc/llc_input.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index c40c9b2..6ef80fe 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -117,9 +117,12 @@ static inline int llc_fixup_skb(struct sk_buff *skb)
skb_pull(skb, llc_len);
if (skb->protocol == htons(ETH_P_802_2)) {
__be16 pdulen = eth_hdr(skb)->h_proto;
- u16 data_size = ntohs(pdulen) - llc_len;
+ s32 data_size = ntohs(pdulen) - llc_len;
- if (unlikely(pskb_trim_rcsum(skb, data_size)))
+ if (data_size < 0
+ || ((skb->tail - (u8 *)pdu) - llc_len) < data_size)
+ return 0;
+ if (unlikely(pskb_trim_rcsum(skb, (unsigned int)data_size)))
return 0;
}
return 1;
--
1.5.4
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