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rose: limit sk_filter trim to payload

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Sockets can have a filter program attached that drops or trims
incoming packets based on the filter program return value.

Rose requires data packets to have at least ROSE_MIN_LEN bytes. It
verifies this on arrival in rose_route_frame and unconditionally pulls
the bytes in rose_recvmsg. The filter can trim packets to below this
value in-between, causing pull to fail, leaving the partial header at
the time of skb_copy_datagram_msg.

Place a lower bound on the size to which sk_filter may trim packets
by introducing sk_filter_trim_cap and call this for rose packets.

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 18:18:56 -04:00
committed by David S. Miller
parent 22cb99fb76
commit f4979fcea7
3 changed files with 12 additions and 7 deletions
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3
net/rose/rose_in.c
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@@ -164,7 +164,8 @@ static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int framety
rose_frames_acked(sk, nr);
if (ns == rose->vr) {
rose_start_idletimer(sk);
if (sock_queue_rcv_skb(sk, skb) == 0) {
if (sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN) == 0 &&
__sock_queue_rcv_skb(sk, skb) == 0) {
rose->vr = (rose->vr + 1) % ROSE_MODULUS;
queued = 1;
} else {