| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 68/98] can: kvaser_usb: Dont free packets when tight on URBs | Date | Sun, 25 Jan 2015 10:07:26 -0800 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: "Ahmed S. Darwish" <ahmed.darwish@valeo.com>
commit b442723fcec445fb0ae1104888dd22cd285e0a91 upstream.
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.
Note:
Finding no more URBs/transmit-contexts and returning NETDEV_TX_BUSY is a driver bug in and out of itself: it means that our start/stop queue flow control is broken.
This patch only fixes the (buggy) error handling code; the root cause shall be fixed in a later commit.
Acked-by: Olivier Sobrie <olivier@sobrie.be> Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/net/can/usb/kvaser_usb.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
--- a/drivers/net/can/usb/kvaser_usb.c +++ b/drivers/net/can/usb/kvaser_usb.c @@ -1285,12 +1285,14 @@ static netdev_tx_t kvaser_usb_start_xmit if (!urb) { netdev_err(netdev, "No memory left for URBs\n"); stats->tx_dropped++; - goto nourbmem; + dev_kfree_skb(skb); + return NETDEV_TX_OK; } buf = kmalloc(sizeof(struct kvaser_msg), GFP_ATOMIC); if (!buf) { stats->tx_dropped++; + dev_kfree_skb(skb); goto nobufmem; } @@ -1325,6 +1327,7 @@ static netdev_tx_t kvaser_usb_start_xmit } } + /* This should never happen; it implies a flow control bug */ if (!context) { netdev_warn(netdev, "cannot find free context\n"); ret = NETDEV_TX_BUSY; @@ -1355,9 +1358,6 @@ static netdev_tx_t kvaser_usb_start_xmit 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) */ - atomic_dec(&priv->active_tx_urbs); usb_unanchor_urb(urb); @@ -1379,8 +1379,6 @@ releasebuf: kfree(buf); nobufmem: usb_free_urb(urb); -nourbmem: - dev_kfree_skb(skb); return ret; }
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