Re: [PATCH] Netvsc: Call hv_unmap_memory() in the netvsc_device_remove()

[Tianyu Lan]

On 2/3/2022 1:05 AM, Michael Kelley (LINUX) wrote:
> From: Tianyu Lan<ltykernel@xxxxxxxxx>  Sent: Tuesday, February 1, 2022 8:32 AM
> > netvsc_device_remove() calls vunmap() inside which should not be
> > called in the interrupt context. Current code calls hv_unmap_memory()
> > in the free_netvsc_device() which is rcu callback and maybe called
> > in the interrupt context. This will trigger BUG_ON(in_interrupt())
> > in the vunmap(). Fix it via moving hv_unmap_memory() to netvsc_device_
> > remove().
> I think this change can fail to call hv_unmap_memory() in an error case.
>
> If netvsc_init_buf() fails after hv_map_memory() succeeds for the receive
> buffer or for the send buffer, no corresponding hv_unmap_memory() will
> be done.  The failure in netvsc_init_buf() will cause netvsc_connect_vsp()
> to fail, so netvsc_add_device() will "goto close" where free_netvsc_device()
> will be called.  But free_netvsc_device() no longer calls hv_unmap_memory(),
> so it won't ever happen.   netvsc_device_remove() is never called in this case
> because netvsc_add_device() failed.

Hi Michael:
      Thanks for your review. Nice catch and will fix in the next
version.