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    Subject[PATCH 5.10 047/157] vhost_vdpa: fix the missing irq_bypass_unregister_producer() invocation
    Date
    From: Gautam Dawar <gdawar.xilinx@gmail.com>

    commit 4c050286bb202cffd5467c1cba982dff391d62e1 upstream.

    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.xilinx@gmail.com>
    Acked-by: Jason Wang <jasowang@redhat.com>
    Link: https://lore.kernel.org/r/20210224114845.104173-1-gdawar.xilinx@gmail.com
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/vhost/vdpa.c | 8 ++------
    1 file changed, 2 insertions(+), 6 deletions(-)

    --- a/drivers/vhost/vdpa.c
    +++ b/drivers/vhost/vdpa.c
    @@ -910,14 +910,10 @@ err:

    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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