Re: [PATCH v2] vhost vdpa: fix the missing irq_bypass_unregister_producer() invocation

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gautam Dawar <gdawar.xilinx@gmail.com>
Cc: martinh@xilinx.com, hanand@xilinx.com, gdawar@xilinx.com,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v2] vhost vdpa: fix the missing irq_bypass_unregister_producer() invocation
Date: Tue, 23 Feb 2021 07:12:54 -0500	[thread overview]
Message-ID: <20210223071149-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAJ-rMYpFFD0vwERMbj_tMLmeFqECr0Q+s4ct_sO0AAt3rgWG0Q@mail.gmail.com>

On Tue, Feb 23, 2021 at 03:30:45PM +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.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211711
> Signed-off-by: Gautam Dawar <gdawar@xilinx.com>

Could you please repost without HTML? Otherwise git am fails on this patch:

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

Also, which commit introduces the bug? A Fixes: tag would be helpful.

Thanks!

> -----
> changelog:
> 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)

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