From 2283f79b22684d2812e5c76fc2280aae00390365 Mon Sep 17 00:00:00 2001 From: Vincent Mailhol Date: Sat, 3 Oct 2020 00:41:45 +0900 Subject: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context If a driver calls can_get_echo_skb() during a hardware IRQ (which is often, but not always, the case), the 'WARN_ON(in_irq)' in net/core/skbuff.c#skb_release_head_state() might be triggered, under network congestion circumstances, together with the potential risk of a NULL pointer dereference. The root cause of this issue is the call to kfree_skb() instead of dev_kfree_skb_irq() in net/core/dev.c#enqueue_to_backlog(). This patch prevents the skb to be freed within the call to netif_rx() by incrementing its reference count with skb_get(). The skb is finally freed by one of the in-irq-context safe functions: dev_consume_skb_any() or dev_kfree_skb_any(). The "any" version is used because some drivers might call can_get_echo_skb() in a normal context. The reason for this issue to occur is that initially, in the core network stack, loopback skb were not supposed to be received in hardware IRQ context. The CAN stack is an exeption. This bug was previously reported back in 2017 in [1] but the proposed patch never got accepted. While [1] directly modifies net/core/dev.c, we try to propose here a smoother modification local to CAN network stack (the assumption behind is that only CAN devices are affected by this issue). [1] http://lore.kernel.org/r/57a3ffb6-3309-3ad5-5a34-e93c3fe3614d@cetitec.com Signed-off-by: Vincent Mailhol Link: https://lore.kernel.org/r/20201002154219.4887-2-mailhol.vincent@wanadoo.fr Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface") Signed-off-by: Marc Kleine-Budde --- drivers/net/can/dev.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'drivers/net/can/dev.c') diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index b70ded3760f2..73cfcd7e9517 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -538,7 +538,11 @@ unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx) if (!skb) return 0; - netif_rx(skb); + skb_get(skb); + if (netif_rx(skb) == NET_RX_SUCCESS) + dev_consume_skb_any(skb); + else + dev_kfree_skb_any(skb); return len; } -- cgit From ed3320cec279407a86bc4c72edc4a39eb49165ec Mon Sep 17 00:00:00 2001 From: Oliver Hartkopp Date: Tue, 20 Oct 2020 08:44:43 +0200 Subject: can: dev: __can_get_echo_skb(): fix real payload length return value for RTR frames The can_get_echo_skb() function returns the number of received bytes to be used for netdev statistics. In the case of RTR frames we get a valid (potential non-zero) data length value which has to be passed for further operations. But on the wire RTR frames have no payload length. Therefore the value to be used in the statistics has to be zero for RTR frames. Reported-by: Vincent Mailhol Signed-off-by: Oliver Hartkopp Link: https://lore.kernel.org/r/20201020064443.80164-1-socketcan@hartkopp.net Fixes: cf5046b309b3 ("can: dev: let can_get_echo_skb() return dlc of CAN frame") Signed-off-by: Marc Kleine-Budde --- drivers/net/can/dev.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/net/can/dev.c') diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 73cfcd7e9517..6dee4f8f2024 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -512,9 +512,13 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr) */ struct sk_buff *skb = priv->echo_skb[idx]; struct canfd_frame *cf = (struct canfd_frame *)skb->data; - u8 len = cf->len; - *len_ptr = len; + /* get the real payload length for netdev statistics */ + if (cf->can_id & CAN_RTR_FLAG) + *len_ptr = 0; + else + *len_ptr = cf->len; + priv->echo_skb[idx] = NULL; return skb; -- cgit