> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuzn...@redhat.com]
> Sent: Wednesday, February 4, 2015 1:01 AM
> To: KY Srinivasan; de...@linuxdriverproject.org
> Cc: Haiyang Zhang; linux-kernel@vger.kernel.org; Dexuan Cui; Jason Wang
> Subject: [PATCH 3/4] Drivers: hv: vmbus: protect vmbus_get_outgoing_channel()
> against channel removal
>
> list_for_each_safe() we have in vmbus_get_outgoing_channel() works, however,
> we
> are not protected against the channel being removed (e.g. after receiving
> rescind
> offer). Users of this function (storvsc_do_io() is the only one at this
> moment)
> can get a link to an already freed channel. Make vmbus_get_outgoing_channel()
> search holding primary->lock as child channels are not being freed unless
> they're
> removed from parent's list.
>
> Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
> ---
> drivers/hv/channel_mgmt.c | 10 +++++++---
> drivers/scsi/storvsc_drv.c | 2 ++
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index fdccd16..af6243c 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -881,18 +881,20 @@ cleanup:
> */
> struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel
> *primary)
> {
> - struct list_head *cur, *tmp;
> + struct list_head *cur;
> int cur_cpu;
> struct vmbus_channel *cur_channel;
> struct vmbus_channel *outgoing_channel = primary;
> int cpu_distance, new_cpu_distance;
> + unsigned long flags;
>
> if (list_empty(&primary->sc_list))
> - return outgoing_channel;
> + return vmbus_get_channel(outgoing_channel);
>
> cur_cpu = hv_context.vp_index[get_cpu()];
> put_cpu();
> - list_for_each_safe(cur, tmp, &primary->sc_list) {
> + spin_lock_irqsave(&primary->lock, flags);
hmm, we should avoid the locking here because it's a performance killer...
How about adding vmbus_get/put_channel() in vmbus_open/close()?
Thanks,
-- Dexuan
> + list_for_each(cur, &primary->sc_list) {
> cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
> if (cur_channel->state != CHANNEL_OPENED_STATE)
> continue;
> @@ -913,6 +915,8 @@ struct vmbus_channel
> *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
>
> outgoing_channel = cur_channel;
> }
> + outgoing_channel = vmbus_get_channel(outgoing_channel);
> + spin_unlock_irqrestore(&primary->lock, flags);
>
> return outgoing_channel;
> }
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 4cff0dd..3b9b851 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1370,6 +1370,8 @@ static int storvsc_do_io(struct hv_device *device,
>
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> }
>
> + vmbus_put_channel(outgoing_channel);
> +
> if (ret != 0)
> return ret;
>
> --
> 1.9.3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
