can: fix multiple delivery of a single CAN frame for overlapping CAN filters

The CAN_RAW socket can set multiple CAN identifier specific filters that lead
to multiple filters in the af_can.c filter processing. These filters are
indenpendent from each other which leads to logical OR'ed filters when applied.

This patch makes sure that every CAN frame which is filtered for a specific
socket is only delivered once to the user space. This is independent from the
number of matching CAN filters of this socket.

As the raw_rcv() function is executed from NET_RX softirq the introduced
variables are implemented as per-CPU variables to avoid extensive locking at
CAN frame reception time.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 21 insertions, 0 deletions

diff --git a/net/can/raw.c b/net/can/raw.c
index 63ffdb0f3a23..0c8d537b59b8 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -74,6 +74,11 @@ MODULE_ALIAS("can-proto-1");
  * storing the single filter in dfilter, to avoid using dynamic memory.
  */
 
+struct uniqframe {
+        ktime_t tstamp;
+        const struct sk_buff *skb;
+};
+
 struct raw_sock {
         struct sock sk;
         int bound;
@@ -86,6 +91,7 @@ struct raw_sock {
         struct can_filter dfilter; /* default/single filter */
         struct can_filter *filter; /* pointer to filter(s) */
         can_err_mask_t err_mask;
+        struct uniqframe __percpu *uniq;
 };
 
 /*
@@ -123,6 +129,15 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
         if (!ro->fd_frames && oskb->len != CAN_MTU)
                 return;
 
+        /* eliminate multiple filter matches for the same skb */
+        if (this_cpu_ptr(ro->uniq)->skb == oskb &&
+            ktime_equal(this_cpu_ptr(ro->uniq)->tstamp, oskb->tstamp)) {
+                return;
+        } else {
+                this_cpu_ptr(ro->uniq)->skb = oskb;
+                this_cpu_ptr(ro->uniq)->tstamp = oskb->tstamp;
+        }
+
         /* clone the given skb to be able to enqueue it into the rcv queue */
         skb = skb_clone(oskb, GFP_ATOMIC);
         if (!skb)
@@ -297,6 +312,11 @@ static int raw_init(struct sock *sk)
         ro->recv_own_msgs    = 0;
         ro->fd_frames        = 0;
 
+        /* alloc_percpu provides zero'ed memory */
+        ro->uniq = alloc_percpu(struct uniqframe);
+        if (unlikely(!ro->uniq))
+                return -ENOMEM;
+
         /* set notifier */
         ro->notifier.notifier_call = raw_notifier;
 
@@ -339,6 +359,7 @@ static int raw_release(struct socket *sock)
         ro->ifindex = 0;
         ro->bound   = 0;
         ro->count   = 0;
+        free_percpu(ro->uniq);
 
         sock_orphan(sk);
         sock->sk = NULL;