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

On Tue, 23 Feb 2021 at 17:43, Michael S. Tsirkin [off-list ref] wrote:

On Tue, Feb 23, 2021 at 03:30:45PM +0530, Gautam Dawar wrote:

quoted

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 <redacted>

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!

I've added the fixes tag and submitted patch v3 in plain-text format.
Thanks,
Gautam

quoted

-----
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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