Virtualization - Feb 2021 - [PATCH v3] vhost_vdpa: fix the missing irq_bypass_unregister_producer() invocation

When qemu with vhost-vdpa netdevice is run for the first time, it works well.
But after the VM is powered off, the next qemu run causes kernel panic due to a
NULL pointer dereference in irq_bypass_register_producer().

When the VM is powered off, vhost_vdpa_clean_irq() misses on calling
irq_bypass_unregister_producer() for irq 0 because of the existing check.

This leaves stale producer nodes, which are reset in vhost_vring_call_reset()
when vhost_dev_init() is invoked during the second qemu run.

As the node member of struct irq_bypass_producer is also initialized
to zero, traversal on the producers list causes crash due to NULL pointer
dereference.

Fixes: 2cf1ba9a4d15c ("vhost_vdpa: implement IRQ offloading in
vhost_vdpa")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211711
Signed-off-by: Gautam Dawar <gdawar at xilinx.com>

-----
changelog:
v2->v3:
 - Re-submitting the patch in plain text format as suggested by Michael
 - Added the fixes tag

v1->v2:
 - Addressed Jason's comment to remove the irq check and use
   vhost_vdpa_unsetup_vq_irq() to avoid local variable vq
-----


diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 62a9bb0efc55..e00573b87aba 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -844,14 +844,10 @@ static int vhost_vdpa_open(struct inode *inode,
struct file *filep)

 static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
 {
-       struct vhost_virtqueue *vq;
        int i;

-       for (i = 0; i < v->nvqs; i++) {
-               vq = &v->vqs[i];
-               if (vq->call_ctx.producer.irq)
-                      
irq_bypass_unregister_producer(&vq->call_ctx.producer);
-       }
+       for (i = 0; i < v->nvqs; i++)
+               vhost_vdpa_unsetup_vq_irq(v, i);
 }

 static int vhost_vdpa_release(struct inode *inode, struct file *filep)

On Tue, Feb 23, 2021 at 06:15:07PM +0530, Gautam Dawar
wrote:
> When qemu with vhost-vdpa netdevice is run for the first time, it works
well.
> But after the VM is powered off, the next qemu run causes kernel panic due
to a
> NULL pointer dereference in irq_bypass_register_producer().
> 
> When the VM is powered off, vhost_vdpa_clean_irq() misses on calling
> irq_bypass_unregister_producer() for irq 0 because of the existing check.
> 
> This leaves stale producer nodes, which are reset in
vhost_vring_call_reset()
> when vhost_dev_init() is invoked during the second qemu run.
> 
> As the node member of struct irq_bypass_producer is also initialized
> to zero, traversal on the producers list causes crash due to NULL pointer
> dereference.
> 
> Fixes: 2cf1ba9a4d15c ("vhost_vdpa: implement IRQ offloading in
vhost_vdpa")
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211711
> Signed-off-by: Gautam Dawar <gdawar at xilinx.com>

A bit better but still:
Applying: vhost_vdpa: fix the missing irq_bypass_unregister_producer()
invocation
error: corrupt patch at line 6
error: could not build fake ancestor
Patch failed at 0001 vhost_vdpa: fix the missing
irq_bypass_unregister_producer() invocation
hint: Use 'git am --show-current-patch=diff' to see the failed patch


you also want to include acks you got on the previous versions.
> -----
> changelog:
> v2->v3:
>  - Re-submitting the patch in plain text format as suggested by Michael
>  - Added the fixes tag
> 
> v1->v2:
>  - Addressed Jason's comment to remove the irq check and use
>    vhost_vdpa_unsetup_vq_irq() to avoid local variable vq
> -----
> 
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 62a9bb0efc55..e00573b87aba 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -844,14 +844,10 @@ static int vhost_vdpa_open(struct inode *inode,
> struct file *filep)
> 
>  static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
>  {
> -       struct vhost_virtqueue *vq;
>         int i;
> 
> -       for (i = 0; i < v->nvqs; i++) {
> -               vq = &v->vqs[i];
> -               if (vq->call_ctx.producer.irq)
> -                      
irq_bypass_unregister_producer(&vq->call_ctx.producer);
> -       }
> +       for (i = 0; i < v->nvqs; i++)
> +               vhost_vdpa_unsetup_vq_irq(v, i);
>  }
> 
>  static int vhost_vdpa_release(struct inode *inode, struct file *filep)