[V3,2/2] virtio-net: sanitize buggy features advertised by host
diff mbox series

Message ID 1416215838-21700-2-git-send-email-jasowang@redhat.com
State New, archived
Headers show
Series
  • [V3,1/2] virtio: introduce methods of sanitizing device features
Related show

Commit Message

Jason Wang Nov. 17, 2014, 9:17 a.m. UTC
This patch tries to detect the possible buggy features advertised by host
and sanitize them. One example is booting virtio-net with only ctrl_vq
disabled, qemu may still advertise many features which depends on it. This
will trigger several BUG()s in virtnet_send_command().

This patch utilizes the sanitize_features() method, and disables all
features that depends on ctrl_vq if it was not advertised.

This fixes the crash when booting with ctrl_vq=off using qemu.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes from V1:
- fix the cut-and-paste error
Changes from V2:
- loop through an array of feature bits
- switch to use dev_warn()
---
 drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Comments

Michael S. Tsirkin Nov. 17, 2014, 10:08 a.m. UTC | #1
On Mon, Nov 17, 2014 at 05:17:18PM +0800, Jason Wang wrote:
> This patch tries to detect the possible buggy features advertised by host
> and sanitize them. One example is booting virtio-net with only ctrl_vq
> disabled, qemu may still advertise many features which depends on it. This
> will trigger several BUG()s in virtnet_send_command().
> 
> This patch utilizes the sanitize_features() method, and disables all
> features that depends on ctrl_vq if it was not advertised.
> 
> This fixes the crash when booting with ctrl_vq=off using qemu.
> 
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>


So I'm not sure this is useful.
The spec says:
	The device MUST NOT offer a feature which requires another feature which
	was not offered.
So this is a buggy hypervisor, and I believe we should just fail probe.
This can be done without crashing, and is generally a better
idea that second-guessing what hypervisor wants us to do.





However, assuming that we do want this change:
This can be replaced with a table driven design in virtio core, but
since you chose to open code it, I would drop table below altogether.


Just make it
	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_RX);
		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_VLAN);
		virtio_disable_feature(dev, VIRTIO_NET_F_GUEST_ANNOUNCE);
		virtio_disable_feature(dev, VIRTIO_NET_F_MQ);
		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR);
	}




> ---
> Changes from V1:
> - fix the cut-and-paste error
> Changes from V2:
> - loop through an array of feature bits
> - switch to use dev_warn()
> ---
>  drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ec2a8b4..6fadd8c 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1948,6 +1948,31 @@ static int virtnet_restore(struct virtio_device *vdev)
>  }
>  #endif
>  
> +static void virtnet_sanitize_features(struct virtio_device *dev)
> +{
> +	unsigned int features_for_ctrl_vq[] = {
> +		VIRTIO_NET_F_CTRL_RX,
> +		VIRTIO_NET_F_CTRL_VLAN,
> +		VIRTIO_NET_F_GUEST_ANNOUNCE,
> +		VIRTIO_NET_F_MQ,
> +		VIRTIO_NET_F_CTRL_MAC_ADDR
> +	};

This is not the only dependency: checksums
have dependencies too. See virtio 1.0 spec.



> +	int i;
> +
> +	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
> +		for (i = 0; i < ARRAY_SIZE(features_for_ctrl_vq); i++) {
> +			unsigned int f = features_for_ctrl_vq[i];
> +			if (virtio_has_feature(dev, f)) {
> +				virtio_disable_feature(dev, f);
> +				dev_warn(&dev->dev,
> +					 "buggy hyperviser: disable feature "
> +					 "0x%x since VIRTIO_NET_F_CTRL_VQ was "
> +					 "not advertised.\n", f);
> +			}
> +		}
> +	}
> +}
> +
>  static struct virtio_device_id id_table[] = {
>  	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
>  	{ 0 },
> @@ -1975,6 +2000,7 @@ static struct virtio_driver virtio_net_driver = {
>  	.probe =	virtnet_probe,
>  	.remove =	virtnet_remove,
>  	.config_changed = virtnet_config_changed,
> +	.sanitize_features = virtnet_sanitize_features,
>  #ifdef CONFIG_PM_SLEEP
>  	.freeze =	virtnet_freeze,
>  	.restore =	virtnet_restore,
> -- 
> 1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
Jason Wang Nov. 18, 2014, 3:03 a.m. UTC | #2
On 11/17/2014 06:08 PM, Michael S. Tsirkin wrote:
> On Mon, Nov 17, 2014 at 05:17:18PM +0800, Jason Wang wrote:
>> This patch tries to detect the possible buggy features advertised by host
>> and sanitize them. One example is booting virtio-net with only ctrl_vq
>> disabled, qemu may still advertise many features which depends on it. This
>> will trigger several BUG()s in virtnet_send_command().
>>
>> This patch utilizes the sanitize_features() method, and disables all
>> features that depends on ctrl_vq if it was not advertised.
>>
>> This fixes the crash when booting with ctrl_vq=off using qemu.
>>
>> Cc: Rusty Russell <rusty@rustcorp.com.au>
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
>> Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>
> So I'm not sure this is useful.
> The spec says:
> 	The device MUST NOT offer a feature which requires another feature which
> 	was not offered.

We can't guarantee that hypervisor's implementation are 100% correct.
> So this is a buggy hypervisor, and I believe we should just fail probe.
> This can be done without crashing, and is generally a better
> idea that second-guessing what hypervisor wants us to do.
>

So we still need something like this patch to detect the wrong
dependencies. And the features fixing like this is not something new,
see how net device fix the features through ndo_fix_features().
>
>
>
> However, assuming that we do want this change:
> This can be replaced with a table driven design in virtio core, but
> since you chose to open code it, I would drop table below altogether.
>
>
> Just make it
> 	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
> 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_RX);
> 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_VLAN);
> 		virtio_disable_feature(dev, VIRTIO_NET_F_GUEST_ANNOUNCE);
> 		virtio_disable_feature(dev, VIRTIO_NET_F_MQ);
> 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR);
> 	}
>

This is similar to what I did in v1 and v2. Either are ok for me.
>
>
>> ---
>> Changes from V1:
>> - fix the cut-and-paste error
>> Changes from V2:
>> - loop through an array of feature bits
>> - switch to use dev_warn()
>> ---
>>  drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++++
>>  1 file changed, 26 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index ec2a8b4..6fadd8c 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1948,6 +1948,31 @@ static int virtnet_restore(struct virtio_device *vdev)
>>  }
>>  #endif
>>  
>> +static void virtnet_sanitize_features(struct virtio_device *dev)
>> +{
>> +	unsigned int features_for_ctrl_vq[] = {
>> +		VIRTIO_NET_F_CTRL_RX,
>> +		VIRTIO_NET_F_CTRL_VLAN,
>> +		VIRTIO_NET_F_GUEST_ANNOUNCE,
>> +		VIRTIO_NET_F_MQ,
>> +		VIRTIO_NET_F_CTRL_MAC_ADDR
>> +	};
> This is not the only dependency: checksums
> have dependencies too. See virtio 1.0 spec.
>

I see ,and this kind of check could be added. But we're really safe
since qemu handle such cases and won't advertise any offload feature is
csum is not supported.
>
>> +	int i;
>> +
>> +	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
>> +		for (i = 0; i < ARRAY_SIZE(features_for_ctrl_vq); i++) {
>> +			unsigned int f = features_for_ctrl_vq[i];
>> +			if (virtio_has_feature(dev, f)) {
>> +				virtio_disable_feature(dev, f);
>> +				dev_warn(&dev->dev,
>> +					 "buggy hyperviser: disable feature "
>> +					 "0x%x since VIRTIO_NET_F_CTRL_VQ was "
>> +					 "not advertised.\n", f);
>> +			}
>> +		}
>> +	}
>> +}
>> +
>>  static struct virtio_device_id id_table[] = {
>>  	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
>>  	{ 0 },
>> @@ -1975,6 +2000,7 @@ static struct virtio_driver virtio_net_driver = {
>>  	.probe =	virtnet_probe,
>>  	.remove =	virtnet_remove,
>>  	.config_changed = virtnet_config_changed,
>> +	.sanitize_features = virtnet_sanitize_features,
>>  #ifdef CONFIG_PM_SLEEP
>>  	.freeze =	virtnet_freeze,
>>  	.restore =	virtnet_restore,
>> -- 
>> 1.9.1
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
Michael S. Tsirkin Nov. 18, 2014, 11:02 a.m. UTC | #3
On Tue, Nov 18, 2014 at 11:03:32AM +0800, Jason Wang wrote:
> On 11/17/2014 06:08 PM, Michael S. Tsirkin wrote:
> > On Mon, Nov 17, 2014 at 05:17:18PM +0800, Jason Wang wrote:
> >> This patch tries to detect the possible buggy features advertised by host
> >> and sanitize them. One example is booting virtio-net with only ctrl_vq
> >> disabled, qemu may still advertise many features which depends on it. This
> >> will trigger several BUG()s in virtnet_send_command().
> >>
> >> This patch utilizes the sanitize_features() method, and disables all
> >> features that depends on ctrl_vq if it was not advertised.
> >>
> >> This fixes the crash when booting with ctrl_vq=off using qemu.
> >>
> >> Cc: Rusty Russell <rusty@rustcorp.com.au>
> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> >> Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >
> > So I'm not sure this is useful.
> > The spec says:
> > 	The device MUST NOT offer a feature which requires another feature which
> > 	was not offered.
> 
> We can't guarantee that hypervisor's implementation are 100% correct.
> > So this is a buggy hypervisor, and I believe we should just fail probe.
> > This can be done without crashing, and is generally a better
> > idea that second-guessing what hypervisor wants us to do.
> >
> 
> So we still need something like this patch to detect the wrong
> dependencies. And the features fixing like this is not something new,
> see how net device fix the features through ndo_fix_features().

I think that's different. If linux refuses to work with a broken
hardware NIC, you can not do anything, and hardware is mass-produced so
we know many people are affected.
If linux refuses to work with a misconfigured hypervisor, it's just one
user who misconfigured it, and hypervisor can be fixed.

So let's not work around bugs at least unless we know that many people
already use a broken hypervisor, something prevents vendor from fixing it.


> >
> >
> >
> > However, assuming that we do want this change:
> > This can be replaced with a table driven design in virtio core, but
> > since you chose to open code it, I would drop table below altogether.
> >
> >
> > Just make it
> > 	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
> > 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_RX);
> > 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_VLAN);
> > 		virtio_disable_feature(dev, VIRTIO_NET_F_GUEST_ANNOUNCE);
> > 		virtio_disable_feature(dev, VIRTIO_NET_F_MQ);
> > 		virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR);
> > 	}
> >
> 
> This is similar to what I did in v1 and v2. Either are ok for me.
> >
> >
> >> ---
> >> Changes from V1:
> >> - fix the cut-and-paste error
> >> Changes from V2:
> >> - loop through an array of feature bits
> >> - switch to use dev_warn()
> >> ---
> >>  drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++++
> >>  1 file changed, 26 insertions(+)
> >>
> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >> index ec2a8b4..6fadd8c 100644
> >> --- a/drivers/net/virtio_net.c
> >> +++ b/drivers/net/virtio_net.c
> >> @@ -1948,6 +1948,31 @@ static int virtnet_restore(struct virtio_device *vdev)
> >>  }
> >>  #endif
> >>  
> >> +static void virtnet_sanitize_features(struct virtio_device *dev)
> >> +{
> >> +	unsigned int features_for_ctrl_vq[] = {
> >> +		VIRTIO_NET_F_CTRL_RX,
> >> +		VIRTIO_NET_F_CTRL_VLAN,
> >> +		VIRTIO_NET_F_GUEST_ANNOUNCE,
> >> +		VIRTIO_NET_F_MQ,
> >> +		VIRTIO_NET_F_CTRL_MAC_ADDR
> >> +	};
> > This is not the only dependency: checksums
> > have dependencies too. See virtio 1.0 spec.
> >
> 
> I see ,and this kind of check could be added. But we're really safe
> since qemu handle such cases and won't advertise any offload feature is
> csum is not supported.
> >
> >> +	int i;
> >> +
> >> +	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
> >> +		for (i = 0; i < ARRAY_SIZE(features_for_ctrl_vq); i++) {
> >> +			unsigned int f = features_for_ctrl_vq[i];
> >> +			if (virtio_has_feature(dev, f)) {
> >> +				virtio_disable_feature(dev, f);
> >> +				dev_warn(&dev->dev,
> >> +					 "buggy hyperviser: disable feature "
> >> +					 "0x%x since VIRTIO_NET_F_CTRL_VQ was "
> >> +					 "not advertised.\n", f);
> >> +			}
> >> +		}
> >> +	}
> >> +}
> >> +
> >>  static struct virtio_device_id id_table[] = {
> >>  	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
> >>  	{ 0 },
> >> @@ -1975,6 +2000,7 @@ static struct virtio_driver virtio_net_driver = {
> >>  	.probe =	virtnet_probe,
> >>  	.remove =	virtnet_remove,
> >>  	.config_changed = virtnet_config_changed,
> >> +	.sanitize_features = virtnet_sanitize_features,
> >>  #ifdef CONFIG_PM_SLEEP
> >>  	.freeze =	virtnet_freeze,
> >>  	.restore =	virtnet_restore,
> >> -- 
> >> 1.9.1
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Patch
diff mbox series

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec2a8b4..6fadd8c 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1948,6 +1948,31 @@  static int virtnet_restore(struct virtio_device *vdev)
 }
 #endif
 
+static void virtnet_sanitize_features(struct virtio_device *dev)
+{
+	unsigned int features_for_ctrl_vq[] = {
+		VIRTIO_NET_F_CTRL_RX,
+		VIRTIO_NET_F_CTRL_VLAN,
+		VIRTIO_NET_F_GUEST_ANNOUNCE,
+		VIRTIO_NET_F_MQ,
+		VIRTIO_NET_F_CTRL_MAC_ADDR
+	};
+	int i;
+
+	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
+		for (i = 0; i < ARRAY_SIZE(features_for_ctrl_vq); i++) {
+			unsigned int f = features_for_ctrl_vq[i];
+			if (virtio_has_feature(dev, f)) {
+				virtio_disable_feature(dev, f);
+				dev_warn(&dev->dev,
+					 "buggy hyperviser: disable feature "
+					 "0x%x since VIRTIO_NET_F_CTRL_VQ was "
+					 "not advertised.\n", f);
+			}
+		}
+	}
+}
+
 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -1975,6 +2000,7 @@  static struct virtio_driver virtio_net_driver = {
 	.probe =	virtnet_probe,
 	.remove =	virtnet_remove,
 	.config_changed = virtnet_config_changed,
+	.sanitize_features = virtnet_sanitize_features,
 #ifdef CONFIG_PM_SLEEP
 	.freeze =	virtnet_freeze,
 	.restore =	virtnet_restore,