linux-kernel - Re: [PATCH v3] drm/vmwgfx: Fix race issue calling pin_user

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Message-ID: <42515e33-3f99-83d5-d14b-3b8e00d97b4a@gmail.com>
Date:   Wed, 9 Nov 2022 17:55:22 +0200
From:   "Martin Krastev (VMware)" <martinkrastev768@...il.com>
To:     Dawei Li <set_pte_at@...look.com>, zackr@...are.com,
        airlied@...il.com, daniel@...ll.ch
Cc:     krastevm@...are.com, linux-graphics-maintainer@...are.com,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3] drm/vmwgfx: Fix race issue calling pin_user_pages

From: Martin Krastev <krastevm@...are.com>


Looks great!


Reviewed-by: Martin Krastev <krastevm@...are.com>


Regards,
Martin


On 9.11.22 г. 17:37 ч., Dawei Li wrote:
> pin_user_pages() is unsafe without protection of mmap_lock,
> fix it by calling pin_user_pages_fast().
>
> Fixes: 7a7a933edd6c ("drm/vmwgfx: Introduce VMware mks-guest-stats")
> Signed-off-by: Dawei Li <set_pte_at@...look.com>
> ---
> v1:
> https://lore.kernel.org/all/TYCP286MB23235C9A9FCF85C045F95EA7CA4F9@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
>
> v1->v2:
> Rebased to latest vmwgfx/drm-misc-fixes.
>
> v2->v3
> Replace pin_user_pages() with pin_user_pages_fast().
> ---
>   drivers/gpu/drm/vmwgfx/vmwgfx_msg.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> index 089046fa21be..50fa3df0bc0c 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> +++ b/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;
>