> -----Original Message----- > From: Mohammed Gamal <mgamal@xxxxxxxxxx> > Sent: Wednesday, September 26, 2018 12:34 PM > To: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx > 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/commit/?id=7b2ee50c0cd513a176a26a71f2989facdd75bfea 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
