Re: [PATCH] can: kvaser_usb: Don't free packets when tight on URBs
From: Olivier Sobrie <hidden>
Date: 2014-12-24 12:31:45
Also in:
linux-can, lkml
Hello Ahmed, On Tue, Dec 23, 2014 at 05:46:54PM +0200, Ahmed S. Darwish wrote:
From: Ahmed S. Darwish <redacted> Flooding the Kvaser CAN to USB dongle with multiple reads and writes in high frequency caused seemingly-random panics in the kernel. On further inspection, it seems the driver erroneously freed the to-be-transmitted packet upon getting tight on URBs and returning NETDEV_TX_BUSY, leading to invalid memory writes and double frees at a later point in time. Signed-off-by: Ahmed S. Darwish <redacted>
Thank you for the fix.
quoted hunk ↗ jump to hunk
--- drivers/net/can/usb/kvaser_usb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (Generated over 3.19.0-rc1)diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c index 541fb7a..34c35d8 100644 --- a/drivers/net/can/usb/kvaser_usb.c +++ b/drivers/net/can/usb/kvaser_usb.c@@ -1286,6 +1286,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb, struct kvaser_msg *msg; int i, err; int ret = NETDEV_TX_OK; + bool kfree_skb_on_error = true; if (can_dropped_invalid_skb(netdev, skb)) return NETDEV_TX_OK;@@ -1336,6 +1337,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb, if (!context) { netdev_warn(netdev, "cannot find free context\n"); + kfree_skb_on_error = false;
Instead of using an extra variable, you can also set skb to NULL here. Or maybe better, you can move the dev_kfree_skb() in the two previous tests (in the check of variables urb and buf). Thank you, Olivier
quoted hunk ↗ jump to hunk
ret = NETDEV_TX_BUSY; goto releasebuf; }@@ -1364,8 +1366,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb, if (unlikely(err)) { can_free_echo_skb(netdev, context->echo_index); - skb = NULL; /* set to NULL to avoid double free in - * dev_kfree_skb(skb) */ + kfree_skb_on_error = false; atomic_dec(&priv->active_tx_urbs); usb_unanchor_urb(urb);@@ -1389,7 +1390,8 @@ releasebuf: nobufmem: usb_free_urb(urb); nourbmem: - dev_kfree_skb(skb); + if (kfree_skb_on_error) + dev_kfree_skb(skb); return ret; }