On Wed, 2018-09-26 at 17:13 +0000, Haiyang Zhang wrote: > > -----Original Message----- > > From: Mohammed Gamal <mgamal@xxxxxxxxxx> > > Sent: Wednesday, September 26, 2018 12:34 PM > > To: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; netdev@vger.kernel. > > org > > Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang > > <haiyangz@xxxxxxxxxxxxx>; vkuznets <vkuznets@xxxxxxxxxx>; > > otubo@xxxxxxxxxx; cavery <cavery@xxxxxxxxxx>; linux- > > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; Mohammed > > Gamal > > <mgamal@xxxxxxxxxx> > > Subject: [PATCH] hv_netvsc: Make sure out channel is fully opened > > on send > > > > Dring high network traffic changes to network interface parameters > > such as > > number of channels or MTU can cause a kernel panic with a NULL > > pointer > > dereference. This is due to netvsc_device_remove() being called and > > deallocating the channel ring buffers, which can then be accessed > > by > > netvsc_send_pkt() before they're allocated on calling > > netvsc_device_add() > > > > The patch fixes this problem by checking the channel state and > > returning > > ENODEV if not yet opened. We also move the call to > > hv_ringbuf_avail_percent() > > which may access the uninitialized ring buffer. > > > > Signed-off-by: Mohammed Gamal <mgamal@xxxxxxxxxx> > > --- > > drivers/net/hyperv/netvsc.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/net/hyperv/netvsc.c > > b/drivers/net/hyperv/netvsc.c index > > fe01e14..75f1b31 100644 > > --- a/drivers/net/hyperv/netvsc.c > > +++ b/drivers/net/hyperv/netvsc.c > > @@ -825,7 +825,12 @@ static inline int netvsc_send_pkt( > > struct netdev_queue *txq = netdev_get_tx_queue(ndev, > > packet->q_idx); > > u64 req_id; > > int ret; > > - u32 ring_avail = > > hv_get_avail_to_write_percent(&out_channel- > > > outbound); > > > > + u32 ring_avail; > > + > > + if (out_channel->state != CHANNEL_OPENED_STATE) > > + return -ENODEV; > > + > > + ring_avail = hv_get_avail_to_write_percent(&out_channel- > > >outbound); > > When you reproducing the NULL ptr panic, does your kernel include the > following patch? > hv_netvsc: common detach logic > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/c > ommit/?id=7b2ee50c0cd513a176a26a71f2989facdd75bfea > Yes it is included. And the commit did reduce the occurrence of this race condition, but it still nevertheless occurs albeit rarely. > We call netif_tx_disable(ndev) and netif_device_detach(ndev) before > doing the changes > on MTU or #channels. So there should be no call to start_xmit() when > channel is not ready. > > If you see the check for CHANNEL_OPENED_STATE is still necessary on > upstream kernel (including > the patch " common detach logic "), we should debug further on the > code and find out the > root cause. > > Thanks, > - Haiyang > _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
