Re: [PATCH 2/4] virtio-mem: Fix probe failed when modprobe virtio_mem

Re: [PATCH 2/4] virtio-mem: Fix probe failed when modprobe virtio_mem

[David Hildenbrand]

On 28.11.22 03:10, Li Zetao wrote:
> When doing the following test steps, an error was found:
>    step 1: modprobe virtio_mem succeeded
>      # modprobe virtio_mem      <-- OK
> 
>    step 2: fault injection in virtio_mem_init()
>      # modprobe -r virtio_mem   <-- OK
>      # ...
>        CPU: 0 PID: 1837 Comm: modprobe Not tainted
>        6.1.0-rc6-00285-g6a1e40c4b995-dirty
>        Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>        Call Trace:
>         <TASK>
>         should_fail.cold+0x5/0x1f
>         ...
>         virtio_mem_init_hotplug+0x9ae/0xe57 [virtio_mem]
>         virtio_mem_init.cold+0x327/0x339 [virtio_mem]
>         virtio_mem_probe+0x48e/0x910 [virtio_mem]
>         virtio_dev_probe+0x608/0xae0
>         ...
>         </TASK>
>        virtio_mem virtio4: could not reserve device region
>        virtio_mem: probe of virtio4 failed with error -16
> 
>    step 3: modprobe virtio_net failed

virtio_net ?

>      # modprobe virtio_mem       <-- failed
>        virtio_mem: probe of virtio4 failed with error -16
> 
> The root cause of the problem is that the virtqueues are not
> stopped on the error handling path when virtio_mem_init()
> fails in virtio_mem_probe(), resulting in an error "-ENOENT"
> returned in the next modprobe call in setup_vq().
> 
> virtio_pci_modern_device uses virtqueues to send or
> receive message, and "queue_enable" records whether the
> queues are available. In vp_modern_find_vqs(), all queues
> will be selected and activated, but once queues are enabled
> there is no way to go back except reset.
> 
> Fix it by reset virtio device on error handling path. After
> virtio_mem_init_vq() succeeded, all virtqueues should be
> stopped on error handling path.
> 
> Fixes: 1fcf0512c9c8 ("virtio_pci: modern driver")

That commit is from 2014. virtio-mem was merged in 2020

Fixes: 5f1f79bbc9e2 ("virtio-mem: Paravirtualized memory hotplug")

> Signed-off-by: Li Zetao <lizetao1@huawei.com>
> ---
>   drivers/virtio/virtio_mem.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
> index 0c2892ec6817..c7f09c2ce982 100644
> --- a/drivers/virtio/virtio_mem.c
> +++ b/drivers/virtio/virtio_mem.c
> @@ -2793,6 +2793,7 @@ static int virtio_mem_probe(struct virtio_device *vdev)
>   
>   	return 0;
>   out_del_vq:
> +	virtio_reset_device(vdev);
>   	vdev->config->del_vqs(vdev);
>   out_free_vm:
>   	kfree(vm);


Apart from that

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb

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Re: [PATCH 3/4] virtio-input: Fix probe failed when modprobe virtio_input

[Michael S. Tsirkin]

On Mon, Nov 28, 2022 at 10:10:04AM +0800, Li Zetao wrote:
> When doing the following test steps, an error was found:
>   step 1: modprobe virtio_input succeeded
>     # modprobe virtio_input      <-- OK
> 
>   step 2: fault injection in input_allocate_device()
>     # modprobe -r virtio_input   <-- OK
>     # ...
>       CPU: 0 PID: 4260 Comm: modprobe Tainted: G        W
>       6.1.0-rc6-00285-g6a1e40c4b995-dirty #109
>       Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>       Call Trace:
>        <TASK>
>        should_fail.cold+0x5/0x1f
>        ...
>        kmalloc_trace+0x27/0xa0
>        input_allocate_device+0x43/0x280
>        virtinput_probe+0x23b/0x1648 [virtio_input]
>        ...
>        </TASK>
>       virtio_input: probe of virtio5 failed with error -12
> 
>   step 3: modprobe virtio_net failed
>     # modprobe virtio_input       <-- failed
>       virtio_input: probe of virtio1 failed with error -2
> 
> The root cause of the problem is that the virtqueues are not
> stopped on the error handling path when input_allocate_device()
> fails in virtinput_probe(), resulting in an error "-ENOENT"
> returned in the next modprobe call in setup_vq().
> 
> virtio_pci_modern_device uses virtqueues to send or
> receive message, and "queue_enable" records whether the
> queues are available. In vp_modern_find_vqs(), all queues
> will be selected and activated, but once queues are enabled
> there is no way to go back except reset.
> 
> Fix it by reset virtio device on error handling path. After
> virtinput_init_vqs() succeeded, all virtqueues should be
> stopped on error handling path.
> 
> Fixes: 1fcf0512c9c8 ("virtio_pci: modern driver")

Probably 271c865161c57cfabca45b93eaa712b19da365bc


> Signed-off-by: Li Zetao <lizetao1@huawei.com>
> ---
>  drivers/virtio/virtio_input.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
> index 3aa46703872d..f638f1cd3531 100644
> --- a/drivers/virtio/virtio_input.c
> +++ b/drivers/virtio/virtio_input.c
> @@ -330,6 +330,7 @@ static int virtinput_probe(struct virtio_device *vdev)
>  err_mt_init_slots:
>  	input_free_device(vi->idev);
>  err_input_alloc:
> +	virtio_reset_device(vdev);
>  	vdev->config->del_vqs(vdev);
>  err_init_vq:
>  	kfree(vi);
> -- 
> 2.25.1

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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Michael S. Tsirkin]

On Mon, Nov 28, 2022 at 10:10:01AM +0800, Li Zetao wrote:
> This patchset fixes similar issue, the root cause of the
> problem is that the virtqueues are not stopped on error
> handling path.

I've been thinking about this.
Almost all drivers are affected.

The reason really is that it used to be the right thing to do:
On legacy pci del_vqs writes 0
into vq index and this resets the device as a side effect
(we actually do this multiple times, what e.g. writes of MSI vector
 after the 1st reset do I have no idea).

mmio ccw and modern pci don't.

Given this has been with us for a while I am inlined to look for
a global solution rather than tweaking each driver.

Given many drivers are supposed to work on legacy too, we know del_vqs
includes a reset for many of them. So I think I see a better way to do
this:

Add virtio_reset_device_and_del_vqs()

and convert all drivers to that.

When doing this, we also need to/can fix a related problem (and related
to the hardening that Jason Wang was looking into):
virtio_reset_device is inherently racy: vq interrupts could
be in flight when we do reset. We need to prevent handlers from firing in
the window between reset and freeing the irq, so we should first
free irqs and only then start changing the state by e.g.
device reset.


Quite a lot of core work here. Jason are you still looking into
hardening?



> Li Zetao (4):
>   9p: Fix probe failed when modprobe 9pnet_virtio
>   virtio-mem: Fix probe failed when modprobe virtio_mem
>   virtio-input: Fix probe failed when modprobe virtio_input
>   virtio-blk: Fix probe failed when modprobe virtio_blk
> 
>  drivers/block/virtio_blk.c    | 1 +
>  drivers/virtio/virtio_input.c | 1 +
>  drivers/virtio/virtio_mem.c   | 1 +
>  net/9p/trans_virtio.c         | 1 +
>  4 files changed, 4 insertions(+)
> 
> -- 
> 2.25.1

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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Jason Wang]

On Mon, Nov 28, 2022 at 6:14 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Nov 28, 2022 at 10:10:01AM +0800, Li Zetao wrote:
> > This patchset fixes similar issue, the root cause of the
> > problem is that the virtqueues are not stopped on error
> > handling path.
>
> I've been thinking about this.
> Almost all drivers are affected.
>
> The reason really is that it used to be the right thing to do:
> On legacy pci del_vqs writes 0
> into vq index

into vq address actually?

> and this resets the device as a side effect

I think there's no guarantee for a device to do this.

> (we actually do this multiple times, what e.g. writes of MSI vector
>  after the 1st reset do I have no idea).
>
> mmio ccw and modern pci don't.
>
> Given this has been with us for a while I am inlined to look for
> a global solution rather than tweaking each driver.

But do we still need patches for -stable at least?

>
> Given many drivers are supposed to work on legacy too, we know del_vqs
> includes a reset for many of them. So I think I see a better way to do
> this:
>
> Add virtio_reset_device_and_del_vqs()

What's the difference with the current del_vqs method? Is this something like:

virtio_reset_device();
config->del_vqs();

>
> and convert all drivers to that.
>
> When doing this, we also need to/can fix a related problem (and related
> to the hardening that Jason Wang was looking into):
> virtio_reset_device is inherently racy: vq interrupts could
> be in flight when we do reset. We need to prevent handlers from firing in
> the window between reset and freeing the irq, so we should first
> free irqs and only then start changing the state by e.g.
> device reset.

Yes.

>
>
> Quite a lot of core work here. Jason are you still looking into
> hardening?

Yes, last time we've discussed a solution that depends on the first
kick to enable the interrupt handler. But after some thought, it seems
risky since there's no guarantee that the device work in this way.

One example is the current vhost_net, it doesn't wait for the kick to
process the rx packets. Any more thought on this?

Thanks


>
>
>
> > Li Zetao (4):
> >   9p: Fix probe failed when modprobe 9pnet_virtio
> >   virtio-mem: Fix probe failed when modprobe virtio_mem
> >   virtio-input: Fix probe failed when modprobe virtio_input
> >   virtio-blk: Fix probe failed when modprobe virtio_blk
> >
> >  drivers/block/virtio_blk.c    | 1 +
> >  drivers/virtio/virtio_input.c | 1 +
> >  drivers/virtio/virtio_mem.c   | 1 +
> >  net/9p/trans_virtio.c         | 1 +
> >  4 files changed, 4 insertions(+)
> >
> > --
> > 2.25.1
>

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Re: [PATCH v2 0/5] Fix probe failed when modprobe modules

[Jens Axboe]

On 11/29/22 9:06 AM, Li Zetao wrote:
> This patchset fixes similar issue, the root cause of the
> problem is that the virtqueues are not stopped on error
> handling path.

Not related to just this patchset, but guys, Huawei really *REALLY* need
to get the email situation sorted. I'm digging whole/half patchsets out
of spam every morning.

This has been brought up in the past. And no, the cloud variant of
the email also doesn't work properly.

Talk to your IT department, get this sorted once and for all. You risk
your patches being dumped on the floor because people don't see them,
or only see small parts of a patchset. And it's really annoying to have
to deal with as a recipient.

-- 
Jens Axboe


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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Michael S. Tsirkin]

On Tue, Nov 29, 2022 at 11:37:09AM +0800, Jason Wang wrote:
> >
> >
> > Quite a lot of core work here. Jason are you still looking into
> > hardening?
> 
> Yes, last time we've discussed a solution that depends on the first
> kick to enable the interrupt handler. But after some thought, it seems
> risky since there's no guarantee that the device work in this way.
> 
> One example is the current vhost_net, it doesn't wait for the kick to
> process the rx packets. Any more thought on this?
> 
> Thanks

Specifically virtio net is careful to call virtio_device_ready
under rtnl lock so buffers are only added after DRIVER_OK.

However we do not need to tie this to kick, this is what I wrote:

> BTW Jason, I had the idea to disable callbacks until driver uses the
> virtio core for the first time (e.g. by calling virtqueue_add* family of
> APIs). Less aggressive than your ideas but I feel it will add security
> to the init path at least.

So not necessarily kick, we can make adding buffers allow the
interrupt.



-- 
MST

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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Jason Wang]

On Mon, Dec 19, 2022 at 6:15 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Nov 29, 2022 at 11:37:09AM +0800, Jason Wang wrote:
> > >
> > >
> > > Quite a lot of core work here. Jason are you still looking into
> > > hardening?
> >
> > Yes, last time we've discussed a solution that depends on the first
> > kick to enable the interrupt handler. But after some thought, it seems
> > risky since there's no guarantee that the device work in this way.
> >
> > One example is the current vhost_net, it doesn't wait for the kick to
> > process the rx packets. Any more thought on this?
> >
> > Thanks
>
> Specifically virtio net is careful to call virtio_device_ready
> under rtnl lock so buffers are only added after DRIVER_OK.

Right but it only got fixed this year after some code audit.

>
> However we do not need to tie this to kick, this is what I wrote:
>
> > BTW Jason, I had the idea to disable callbacks until driver uses the
> > virtio core for the first time (e.g. by calling virtqueue_add* family of
> > APIs). Less aggressive than your ideas but I feel it will add security
> > to the init path at least.
>
> So not necessarily kick, we can make adding buffers allow the
> interrupt.

Some questions:

1) It introduces a code defined behaviour other than depending on the
spec defined behavior like DRIVER_OK, this will lead extra complexity
in auditing
2) there's no guarantee that the interrupt handler is ready before
virtqueue_add(), or it requires barriers before virtqueue_add() to
make sure the handler is commit

So it looks to me the virtio_device_ready() should be still the
correct way to go:

1) it depends on spec defined behaviour like DRIVER_OK, and it then
can comply with possible future security requirement of drivers
defined in the spec
2) choose to use a new boolean instead of reusing vq->broken
3) enable the harden in driver one by one

Does it make sense?

Thanks

>
>
>
> --
> MST
>

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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Michael S. Tsirkin]

On Mon, Nov 28, 2022 at 05:14:44AM -0500, Michael S. Tsirkin wrote:
> On Mon, Nov 28, 2022 at 10:10:01AM +0800, Li Zetao wrote:
> > This patchset fixes similar issue, the root cause of the
> > problem is that the virtqueues are not stopped on error
> > handling path.
> 
> I've been thinking about this.
> Almost all drivers are affected.
> 
> The reason really is that it used to be the right thing to do:
> On legacy pci del_vqs writes 0
> into vq index and this resets the device as a side effect
> (we actually do this multiple times, what e.g. writes of MSI vector
>  after the 1st reset do I have no idea).
> 
> mmio ccw and modern pci don't.
> 
> Given this has been with us for a while I am inlined to look for
> a global solution rather than tweaking each driver.
> 
> Given many drivers are supposed to work on legacy too, we know del_vqs
> includes a reset for many of them. So I think I see a better way to do
> this:
> 
> Add virtio_reset_device_and_del_vqs()
> 
> and convert all drivers to that.
> 
> When doing this, we also need to/can fix a related problem (and related
> to the hardening that Jason Wang was looking into):
> virtio_reset_device is inherently racy: vq interrupts could
> be in flight when we do reset. We need to prevent handlers from firing in
> the window between reset and freeing the irq, so we should first
> free irqs and only then start changing the state by e.g.
> device reset.
> 
> 
> Quite a lot of core work here. Jason are you still looking into
> hardening?
> 

Li Zetao, Jason, any updates. You guys looking into this?


> 
> > Li Zetao (4):
> >   9p: Fix probe failed when modprobe 9pnet_virtio
> >   virtio-mem: Fix probe failed when modprobe virtio_mem
> >   virtio-input: Fix probe failed when modprobe virtio_input
> >   virtio-blk: Fix probe failed when modprobe virtio_blk
> > 
> >  drivers/block/virtio_blk.c    | 1 +
> >  drivers/virtio/virtio_input.c | 1 +
> >  drivers/virtio/virtio_mem.c   | 1 +
> >  net/9p/trans_virtio.c         | 1 +
> >  4 files changed, 4 insertions(+)
> > 
> > -- 
> > 2.25.1

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Re: [PATCH 0/4] Fix probe failed when modprobe modules

[Jason Wang]

On Fri, Jan 27, 2023 at 7:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Nov 28, 2022 at 05:14:44AM -0500, Michael S. Tsirkin wrote:
> > On Mon, Nov 28, 2022 at 10:10:01AM +0800, Li Zetao wrote:
> > > This patchset fixes similar issue, the root cause of the
> > > problem is that the virtqueues are not stopped on error
> > > handling path.
> >
> > I've been thinking about this.
> > Almost all drivers are affected.
> >
> > The reason really is that it used to be the right thing to do:
> > On legacy pci del_vqs writes 0
> > into vq index and this resets the device as a side effect
> > (we actually do this multiple times, what e.g. writes of MSI vector
> >  after the 1st reset do I have no idea).
> >
> > mmio ccw and modern pci don't.
> >
> > Given this has been with us for a while I am inlined to look for
> > a global solution rather than tweaking each driver.
> >
> > Given many drivers are supposed to work on legacy too, we know del_vqs
> > includes a reset for many of them. So I think I see a better way to do
> > this:
> >
> > Add virtio_reset_device_and_del_vqs()
> >
> > and convert all drivers to that.
> >
> > When doing this, we also need to/can fix a related problem (and related
> > to the hardening that Jason Wang was looking into):
> > virtio_reset_device is inherently racy: vq interrupts could
> > be in flight when we do reset. We need to prevent handlers from firing in
> > the window between reset and freeing the irq, so we should first
> > free irqs and only then start changing the state by e.g.
> > device reset.
> >
> >
> > Quite a lot of core work here. Jason are you still looking into
> > hardening?
> >
>
> Li Zetao, Jason, any updates. You guys looking into this?

At least I will continue the work of IRQ hardening. And this work
could be done on top.

Thanks

>
>
> >
> > > Li Zetao (4):
> > >   9p: Fix probe failed when modprobe 9pnet_virtio
> > >   virtio-mem: Fix probe failed when modprobe virtio_mem
> > >   virtio-input: Fix probe failed when modprobe virtio_input
> > >   virtio-blk: Fix probe failed when modprobe virtio_blk
> > >
> > >  drivers/block/virtio_blk.c    | 1 +
> > >  drivers/virtio/virtio_input.c | 1 +
> > >  drivers/virtio/virtio_mem.c   | 1 +
> > >  net/9p/trans_virtio.c         | 1 +
> > >  4 files changed, 4 insertions(+)
> > >
> > > --
> > > 2.25.1
>

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