drm/vmwgfx: Fix race issue calling pin_user_pages

pin_user_pages() is unsafe without protection of mmap_lock,
fix it by calling pin_user_pages_fast().

Fixes: 7a7a933 ("drm/vmwgfx: Introduce VMware mks-guest-stats")
Signed-off-by: Dawei Li <[email protected]>
Reviewed-by: Martin Krastev <[email protected]>
Signed-off-by: Zack Rusin <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/TYWP286MB23193621CB443E1E1959A00BCA3E9@TYWP286MB2319.JPNP286.PROD.OUTLOOK.COM

Author: Dawei Li

drivers/gpu/drm/vmwgfx/vmwgfx_msg.c

@@ -1085,21 +1085,21 @@ int vmw_mksstat_add_ioctl(struct drm_device *dev, void *data,
 	reset_ppn_array(pdesc->strsPPNs, ARRAY_SIZE(pdesc->strsPPNs));
 
 	/* Pin mksGuestStat user pages and store those in the instance descriptor */
-	nr_pinned_stat = pin_user_pages(arg->stat, num_pages_stat, FOLL_LONGTERM, pages_stat, NULL);
+	nr_pinned_stat = pin_user_pages_fast(arg->stat, num_pages_stat, FOLL_LONGTERM, pages_stat);
 	if (num_pages_stat != nr_pinned_stat)
 		goto err_pin_stat;
 
 	for (i = 0; i < num_pages_stat; ++i)
 		pdesc->statPPNs[i] = page_to_pfn(pages_stat[i]);
 
-	nr_pinned_info = pin_user_pages(arg->info, num_pages_info, FOLL_LONGTERM, pages_info, NULL);
+	nr_pinned_info = pin_user_pages_fast(arg->info, num_pages_info, FOLL_LONGTERM, pages_info);
 	if (num_pages_info != nr_pinned_info)
 		goto err_pin_info;
 
 	for (i = 0; i < num_pages_info; ++i)
 		pdesc->infoPPNs[i] = page_to_pfn(pages_info[i]);
 
-	nr_pinned_strs = pin_user_pages(arg->strs, num_pages_strs, FOLL_LONGTERM, pages_strs, NULL);
+	nr_pinned_strs = pin_user_pages_fast(arg->strs, num_pages_strs, FOLL_LONGTERM, pages_strs);
 	if (num_pages_strs != nr_pinned_strs)
 		goto err_pin_strs;