Linux Virtualization - Mar 2017 - [REGRESSION] 07ec51480b5e ("virtio_pci: use shared interrupts for virtqueues") causes crashes in guest

Hi,

Fedora has received multiple reports of crashes when running
4.11 as a guest

https://bugzilla.redhat.com/show_bug.cgi?id=1430297
https://bugzilla.redhat.com/show_bug.cgi?id=1434462
https://bugzilla.kernel.org/show_bug.cgi?id=194911
https://bugzilla.redhat.com/show_bug.cgi?id=1433899

The crashes are not always consistent but they are generally
some flavor of oops or GPF in virtio related code. Multiple people
have done bisections (Thank you Thorsten Leemhuis and 
Richard W.M. Jones) and found this commit to be at fault

07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 is the first bad commit
commit 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507
Author: Christoph Hellwig <hch at lst.de>
Date:   Sun Feb 5 18:15:19 2017 +0100

    virtio_pci: use shared interrupts for virtqueues
    
    This lets IRQ layer handle dispatching IRQs to separate handlers for the
    case where we don't have per-VQ MSI-X vectors, and allows us to greatly
    simplify the code based on the assumption that we always have interrupt
    vector 0 (legacy INTx or config interrupt for MSI-X) available, and
    any other interrupt is request/freed throught the VQ, even if the
    actual interrupt line might be shared in some cases.
    
    This allows removing a great deal of variables keeping track of the
    interrupt state in struct virtio_pci_device, as we can now simply walk the
    list of VQs and deal with per-VQ interrupt handlers there, and only treat
    vector 0 special.
    
    Additionally clean up the VQ allocation code to properly unwind on error
    instead of having a single global cleanup label, which is error prone,
    and in this case also leads to more code.
    
    Signed-off-by: Christoph Hellwig <hch at lst.de>
    Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

:040000 040000 79a8267ffb73f9d244267c5f68365305bddd4696
8832a160b978710bbd24ba6966f462b3faa27fcc M	drivers

It doesn't revert cleanly so we haven't been able to do a clean
test. Any ideas?

Thanks,
Laura

On 2017?03?23? 08:30, Laura Abbott wrote:
> Hi,
>
> Fedora has received multiple reports of crashes when running
> 4.11 as a guest
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1430297
> https://bugzilla.redhat.com/show_bug.cgi?id=1434462
> https://bugzilla.kernel.org/show_bug.cgi?id=194911
> https://bugzilla.redhat.com/show_bug.cgi?id=1433899
>
> The crashes are not always consistent but they are generally
> some flavor of oops or GPF in virtio related code. Multiple people
> have done bisections (Thank you Thorsten Leemhuis and
> Richard W.M. Jones) and found this commit to be at fault
>
> 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 is the first bad commit
> commit 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507
> Author: Christoph Hellwig <hch at lst.de>
> Date:   Sun Feb 5 18:15:19 2017 +0100
>
>      virtio_pci: use shared interrupts for virtqueues
>      
>      This lets IRQ layer handle dispatching IRQs to separate handlers for
the
>      case where we don't have per-VQ MSI-X vectors, and allows us to
greatly
>      simplify the code based on the assumption that we always have
interrupt
>      vector 0 (legacy INTx or config interrupt for MSI-X) available, and
>      any other interrupt is request/freed throught the VQ, even if the
>      actual interrupt line might be shared in some cases.
>      
>      This allows removing a great deal of variables keeping track of the
>      interrupt state in struct virtio_pci_device, as we can now simply walk
the
>      list of VQs and deal with per-VQ interrupt handlers there, and only
treat
>      vector 0 special.
>      
>      Additionally clean up the VQ allocation code to properly unwind on
error
>      instead of having a single global cleanup label, which is error prone,
>      and in this case also leads to more code.
>      
>      Signed-off-by: Christoph Hellwig <hch at lst.de>
>      Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
>
> :040000 040000 79a8267ffb73f9d244267c5f68365305bddd4696
8832a160b978710bbd24ba6966f462b3faa27fcc M	drivers
>
> It doesn't revert cleanly so we haven't been able to do a clean
> test. Any ideas?
>
> Thanks,
> Laura
Hello:

Can you try the attached patch to see if it solves the problem? (At 
least it silent KASan warnings for me).

Thanks


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On Thu, Mar 23, 2017 at 01:13:50PM +0800, Jason Wang
wrote:
>
>
> On 2017?03?23? 08:30, Laura Abbott wrote:
>> Hi,
>>
>> Fedora has received multiple reports of crashes when running
>> 4.11 as a guest
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1430297
>> https://bugzilla.redhat.com/show_bug.cgi?id=1434462
>> https://bugzilla.kernel.org/show_bug.cgi?id=194911
>> https://bugzilla.redhat.com/show_bug.cgi?id=1433899
>>
>> The crashes are not always consistent but they are generally
>> some flavor of oops or GPF in virtio related code. Multiple people
>> have done bisections (Thank you Thorsten Leemhuis and
>> Richard W.M. Jones) and found this commit to be at fault
>>
>> 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 is the first bad commit
>> commit 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507
>> Author: Christoph Hellwig <hch at lst.de>
>> Date:   Sun Feb 5 18:15:19 2017 +0100
>>
>>      virtio_pci: use shared interrupts for virtqueues
>>           This lets IRQ layer handle dispatching IRQs to separate
handlers
>> for the
>>      case where we don't have per-VQ MSI-X vectors, and allows us
to greatly
>>      simplify the code based on the assumption that we always have
interrupt
>>      vector 0 (legacy INTx or config interrupt for MSI-X) available,
and
>>      any other interrupt is request/freed throught the VQ, even if the
>>      actual interrupt line might be shared in some cases.
>>           This allows removing a great deal of variables keeping track
of
>> the
>>      interrupt state in struct virtio_pci_device, as we can now simply
walk the
>>      list of VQs and deal with per-VQ interrupt handlers there, and
only treat
>>      vector 0 special.
>>           Additionally clean up the VQ allocation code to properly
unwind
>> on error
>>      instead of having a single global cleanup label, which is error
prone,
>>      and in this case also leads to more code.
>>           Signed-off-by: Christoph Hellwig <hch at lst.de>
>>      Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
>>
>> :040000 040000 79a8267ffb73f9d244267c5f68365305bddd4696
8832a160b978710bbd24ba6966f462b3faa27fcc M	drivers
>>
>> It doesn't revert cleanly so we haven't been able to do a clean
>> test. Any ideas?
>>
>> Thanks,
>> Laura
>
> Hello:
>
> Can you try the attached patch to see if it solves the problem? (At least 
> it silent KASan warnings for me).
This looks like a correct fix to me, independent of fixing the original
bug or not:

Reviewed-by: Christoph Hellwig <hch at lst.de>

On Thu, Mar 23, 2017 at 01:13:50PM +0800, Jason Wang
wrote:
> >From 312859b596e83a2164a8430343d31fce2a5ad808 Mon Sep 17 00:00:00 2001
> From: Jason Wang <jasowang at redhat.com>
> Date: Thu, 23 Mar 2017 13:07:16 +0800
> Subject: [PATCH] virtio_pci: fix out of bound access for msix_names
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
I tested this, and it does appear to fix the crashes in
vp_modern_find_vqs.  Therefore:

Tested-by: Richard W.M. Jones <rjones at redhat.com>

Thanks,

Rich.
>  drivers/virtio/virtio_pci_common.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
> index df548a6..5905349 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -147,7 +147,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
unsigned nvqs,
>  {
>  	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>  	const char *name = dev_name(&vp_dev->vdev.dev);
> -	int i, err = -ENOMEM, allocated_vectors, nvectors;
> +	int i, j, err = -ENOMEM, allocated_vectors, nvectors;
>  	unsigned flags = PCI_IRQ_MSIX;
>  	bool shared = false;
>  	u16 msix_vec;
> @@ -212,7 +212,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev,
unsigned nvqs,
>  	if (!vp_dev->msix_vector_map)
>  		goto out_disable_config_irq;
>  
> -	allocated_vectors = 1; /* vector 0 is the config interrupt */
> +	allocated_vectors = j = 1; /* vector 0 is the config interrupt */
>  	for (i = 0; i < nvqs; ++i) {
>  		if (!names[i]) {
>  			vqs[i] = NULL;
> @@ -236,18 +236,19 @@ static int vp_find_vqs_msix(struct virtio_device
*vdev, unsigned nvqs,
>  			continue;
>  		}
>  
> -		snprintf(vp_dev->msix_names[i + 1],
> +		snprintf(vp_dev->msix_names[j],
>  			 sizeof(*vp_dev->msix_names), "%s-%s",
>  			 dev_name(&vp_dev->vdev.dev), names[i]);
>  		err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
>  				  vring_interrupt, IRQF_SHARED,
> -				  vp_dev->msix_names[i + 1], vqs[i]);
> +				  vp_dev->msix_names[j], vqs[i]);
>  		if (err) {
>  			/* don't free this irq on error */
>  			vp_dev->msix_vector_map[i] = VIRTIO_MSI_NO_VECTOR;
>  			goto out_remove_vqs;
>  		}
>  		vp_dev->msix_vector_map[i] = msix_vec;
> +		j++;
>  
>  		/*
>  		 * Use a different vector for each queue if they are available,
> -- 
> 2.7.4
> 

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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