Re: [ldv-project] [net] libertas: potential race condition

On Tue, Jun 14, 2016 at 05:16:11PM +0400, Pavel Andrianov wrote:

08.06.2016 02:51, James Cameron пишет:

quoted

On Tue, Jun 07, 2016 at 09:39:55AM -0500, Dan Williams wrote:

quoted

On Tue, 2016-06-07 at 13:30 +0400, Pavel Andrianov wrote:

quoted

Hi!

There is a potential race condition in
drivers/net/wireless/libertas/libertas.ko.
In the function lbs_hard_start_xmit(..), line 159, a socket buffer
is
written to priv->current_skb with a spin_lock protection.
In the function lbs_mac_event_disconnected(..), lines 50-51, the
field
current_skb is cleaned. There is no protection used. The
corresponding
handlers are activated at the same time in lbs_start_card(..) and
then
may be executed simultaneously. Note, there are two structures
lbs_netdev_ops and mesh_netdev_ops, which have the target handler
lbs_hard_start_xmit.
Is it a real race or I have missed something?

Yeah, it looks like it should be grabbing priv->driver_lock before
clearing priv->currenttxskb in lbs_mac_event_disconnected().  Care to
submit a patch after testing?  Do you have any of that hardware?

I've hardware, with serial console.

Can test any patch, on USB (8388) or SDIO (8686).

Hi!

I've prepare the patch for this issue. Could you test it?

Thank you.

Tested on OLPC XO-1 (usb8388) and XO-1.5 (sd8686) with v4.7-rc3.

Confirmed that lbs_mac_event_disconnected is being called on the
station when hostapd on access point is given SIGHUP.

Longer duration test was;

- SSH to station and run "top -d 0.2",

- send SIGHUP every six seconds, for 300 cycles,

You may add my;

Tested-by: James Cameron <redacted>

-- 
James Cameron
http://quozl.netrek.org/