On Tue, 26 Jul 2016, Willem de Bruijn wrote:
I modified the original patch to call sk_filter for ERTM before the packet is
handled by the state machine and to not set the filter locked flag. I tested
using l2test in ERTM mode, with and without a "randomly drop 1 in 64 packets"
filter attached.
Thanks for testing. For consistency's sake, is it preferable to filter
at this point for all modes?
Only ERTM and streaming mode end up on this code path, and I think there's
a benefit to handling these two modes similarly. There are a number of
other paths to l2cap_sock_recv_cb(), and there isn't one perfect place to
call sk_filter for all modes.
Mat
---
net/bluetooth/l2cap_core.c | 4 ++++
net/bluetooth/l2cap_sock.c | 13 +++++++++++--
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 54ceb1f..d5de0ce 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -32,6 +32,7 @@
#include <linux/debugfs.h>
#include <linux/crc16.h>
+#include <linux/filter.h>
#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
@@ -6610,6 +6611,9 @@ static int l2cap_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb)
goto drop;
}
+ if (chan->mode == L2CAP_MODE_ERTM && sk_filter(chan->data, skb))
+ goto drop;
+
sk_filter can also accept, but trim, packets. If the protocol expects
a header that it unconditionally pulls later, use sk_filter_trim to
sk_filter_trim_cap? I see that you added that recently. It's not in
bluetooth-next and we're aiming for a patch that can be easily backported
to stable.
avoid trimming to below header length. I think I saw a path from
l2cap_data_rcv
l2cap_rx
l2cap_rx_state_recv
l2cap_reassemble_sdu
case L2CAP_SAR_START
skb_pull(skb, L2CAP_SDULEN_SIZE)
How about checking skb->len before that skb_pull instead?
--
Mat Martineau
Intel OTC
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