netdev - [PATCH net-next 7/7] can: add drop reasons in CAN protocols receive path

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Message-ID: <20250610094933.1593081-8-mkl@pengutronix.de>
Date: Tue, 10 Jun 2025 11:46:22 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Davide Caratti <dcaratti@...hat.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net-next 7/7] can: add drop reasons in CAN protocols receive path

From: Davide Caratti <dcaratti@...hat.com>

sock_queue_rcv_skb() can fail because of lack of memory resources: use
drop reasons and pass the receiving socket to the tracepoint, so that
it's possible to better locate/debug such events.

Tested with:

| # modprobe vcan echo=1
| # ip link add name vcan2 type vcan
| # ip link set dev vcan2 up
| # ./netlayer/tst-proc 1 &
| # bg
| # while true ; do perf record -e skb:kfree_skb -aR  -- \
| > ./raw/tst-raw-sendto vcan2 ; perf script ; done
| [...]
| tst-raw-sendto 10942 [000] 506428.431856: skb:kfree_skb: skbaddr=0xffff97cec38b4200 rx_sk=0xffff97cf0f75a800 protocol=12 location=raw_rcv+0x20e reason: SOCKET_RCVBUF

Signed-off-by: Davide Caratti <dcaratti@...hat.com>
Link: https://patch.msgid.link/20250604160605.1005704-3-dcaratti@redhat.com
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/bcm.c          | 5 +++--
 net/can/isotp.c        | 5 +++--
 net/can/j1939/socket.c | 5 +++--
 net/can/raw.c          | 5 +++--
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 6bc1cc4c94c5..5e690a2377e4 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -359,6 +359,7 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
 	unsigned int datalen = head->nframes * op->cfsiz;
 	int err;
 	unsigned int *pflags;
+	enum skb_drop_reason reason;
 
 	skb = alloc_skb(sizeof(*head) + datalen, gfp_any());
 	if (!skb)
@@ -413,11 +414,11 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
 	addr->can_family  = AF_CAN;
 	addr->can_ifindex = op->rx_ifindex;
 
-	err = sock_queue_rcv_skb(sk, skb);
+	err = sock_queue_rcv_skb_reason(sk, skb, &reason);
 	if (err < 0) {
 		struct bcm_sock *bo = bcm_sk(sk);
 
-		kfree_skb(skb);
+		sk_skb_reason_drop(sk, skb, reason);
 		/* don't care about overflows in this statistic */
 		bo->dropped_usr_msgs++;
 	}
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 1efa377f002e..dee1412b3c9c 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -278,6 +278,7 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
 static void isotp_rcv_skb(struct sk_buff *skb, struct sock *sk)
 {
 	struct sockaddr_can *addr = (struct sockaddr_can *)skb->cb;
+	enum skb_drop_reason reason;
 
 	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct sockaddr_can));
 
@@ -285,8 +286,8 @@ static void isotp_rcv_skb(struct sk_buff *skb, struct sock *sk)
 	addr->can_family = AF_CAN;
 	addr->can_ifindex = skb->dev->ifindex;
 
-	if (sock_queue_rcv_skb(sk, skb) < 0)
-		kfree_skb(skb);
+	if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0)
+		sk_skb_reason_drop(sk, skb, reason);
 }
 
 static u8 padlen(u8 datalen)
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 6fefe7a68761..3d8b588822f9 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -311,6 +311,7 @@ static void j1939_sk_recv_one(struct j1939_sock *jsk, struct sk_buff *oskb)
 {
 	const struct j1939_sk_buff_cb *oskcb = j1939_skb_to_cb(oskb);
 	struct j1939_sk_buff_cb *skcb;
+	enum skb_drop_reason reason;
 	struct sk_buff *skb;
 
 	if (oskb->sk == &jsk->sk)
@@ -331,8 +332,8 @@ static void j1939_sk_recv_one(struct j1939_sock *jsk, struct sk_buff *oskb)
 	if (skb->sk)
 		skcb->msg_flags |= MSG_DONTROUTE;
 
-	if (sock_queue_rcv_skb(&jsk->sk, skb) < 0)
-		kfree_skb(skb);
+	if (sock_queue_rcv_skb_reason(&jsk->sk, skb, &reason) < 0)
+		sk_skb_reason_drop(&jsk->sk, skb, reason);
 }
 
 bool j1939_sk_recv_match(struct j1939_priv *priv, struct j1939_sk_buff_cb *skcb)
diff --git a/net/can/raw.c b/net/can/raw.c
index 020f21430b1d..76b867d21def 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -129,6 +129,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 {
 	struct sock *sk = (struct sock *)data;
 	struct raw_sock *ro = raw_sk(sk);
+	enum skb_drop_reason reason;
 	struct sockaddr_can *addr;
 	struct sk_buff *skb;
 	unsigned int *pflags;
@@ -205,8 +206,8 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 	if (oskb->sk == sk)
 		*pflags |= MSG_CONFIRM;
 
-	if (sock_queue_rcv_skb(sk, skb) < 0)
-		kfree_skb(skb);
+	if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0)
+		sk_skb_reason_drop(sk, skb, reason);
 }
 
 static int raw_enable_filters(struct net *net, struct net_device *dev,
-- 
2.47.2