Re: [PATCH] mshv_vtl: initialize poll file mutex before device registration

[Wei Liu <wei.liu@kernel.org>]

On Mon, Oct 19, 2026 at 10:31:59AM +0530, Naman Jain wrote:
> 
> 
> On 10/18/2026 9:16 AM, Jiale Yao wrote:
> > mshv_vtl_init() registers /dev/mshv before initializing the poll file
> > mutex. A concurrent MSHV_SET_POLL_FILE ioctl can therefore attempt to lock
> > an uninitialized mutex while module initialization is still in progress.
> > 
> > Initialize the file-scope mutex statically so it is ready before the misc
> > device becomes visible.
> > 
> > Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver")
> > Signed-off-by: Jiale Yao <yaojiale02@163.com>
> > ---
> >   drivers/hv/mshv_vtl_main.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
> > index d8225242c73f..2b40c9e3bf88 100644
> > --- a/drivers/hv/mshv_vtl_main.c
> > +++ b/drivers/hv/mshv_vtl_main.c
> > @@ -95,7 +95,7 @@ union hv_synic_overlay_page_msr {
> >   	} __packed;
> >   };
> > -static struct mutex mshv_vtl_poll_file_lock;
> > +static DEFINE_MUTEX(mshv_vtl_poll_file_lock);
> >   static union hv_register_vsm_page_offsets mshv_vsm_page_offsets;
> >   static union hv_register_vsm_capabilities mshv_vsm_capabilities;
> > @@ -1370,8 +1370,6 @@ static int __init mshv_vtl_init(void)
> >   		goto free_low;
> >   	}
> > -	mutex_init(&mshv_vtl_poll_file_lock);
> > -
> >   	device_initialize(mem_dev);
> >   	dev_set_name(mem_dev, "mshv vtl mem dev");
> >   	ret = device_add(mem_dev);
> 
> While this issue may not happen in practice, as OpenVMM userspace runs much
> later than these init function invocations, but it is good to have the
> potential race condition fixed.
> 
> Reviewed-by: Naman Jain <namjain@linux.microsoft.com>

Applied.