From: Javier Martinez Canillas <javierm@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>,
Andrzej Hajda <andrzej.hajda@intel.com>,
linux-kernel@vger.kernel.org
Cc: linux-fbdev@vger.kernel.org,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Helge Deller <deller@gmx.de>,
dri-devel@lists.freedesktop.org,
Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH v3 1/4] fbdev: Prevent possible use-after-free in fb_release()
Date: Mon, 9 May 2022 22:03:46 +0200 [thread overview]
Message-ID: <2bf27b09-0896-1849-254f-d5b19abdc892@redhat.com> (raw)
In-Reply-To: <b5ab1c49-04e7-36c3-677d-2989b79e50ca@suse.de>
On 5/9/22 20:12, Thomas Zimmermann wrote:
[snip]
>> I actually thought about the same but then remembered what Daniel said in [0]
>> (AFAIU at least) that these should be done in .remove() so the current code
>> looks like matches that and only framebuffer_release() should be moved.
>>
>> For vesafb a previous patch proposed to also move a release_region() call to
>> .fb_destroy() and Daniel also said that it was iffy and shouldn't be done [1].
>>
>> But I'm also not fb expert so happy to move fb_dealloc_cmap() as well if that
>> is the correct thing to do.
>
> The cmap data structure is software state that can be accessed via icotl
> as long as the devfile is open. Drivers update the hardware from it. See
> [1]. Moving that cleanup into fb_destroy seems appropriate to me.
>
I see, that makes sense. Then something like the following instead?
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index d265a73313c9..ce0d89c49e42 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -627,12 +627,6 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
cancel_work_sync(&fb_helper->resume_work);
cancel_work_sync(&fb_helper->damage_work);
- info = fb_helper->fbdev;
- if (info) {
- if (info->cmap.len)
- fb_dealloc_cmap(&info->cmap);
- framebuffer_release(info);
- }
fb_helper->fbdev = NULL;
mutex_lock(&kernel_fb_helper_lock);
@@ -2111,7 +2105,11 @@ static void drm_fbdev_release(struct drm_fb_helper *fb_helper)
*/
static void drm_fbdev_fb_destroy(struct fb_info *info)
{
+ if (info->cmap.len)
+ fb_dealloc_cmap(&info->cmap);
+
drm_fbdev_release(info->par);
+ framebuffer_release(info);
}
static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
--
Best regards,
Javier Martinez Canillas
Linux Engineering
Red Hat
next prev parent reply other threads:[~2022-05-09 20:06 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-05 21:59 [PATCH v3 0/4] fbdev: Fix use-after-free caused by wrong fb_info cleanup in drivers Javier Martinez Canillas
2022-05-05 22:04 ` [PATCH v3 1/4] fbdev: Prevent possible use-after-free in fb_release() Javier Martinez Canillas
2022-05-09 14:56 ` Andrzej Hajda
2022-05-09 15:30 ` Javier Martinez Canillas
2022-05-09 15:51 ` Andrzej Hajda
2022-05-09 16:33 ` Javier Martinez Canillas
2022-05-09 18:12 ` Thomas Zimmermann
2022-05-09 20:03 ` Javier Martinez Canillas [this message]
2022-05-09 22:22 ` Andrzej Hajda
2022-05-09 22:42 ` Javier Martinez Canillas
2022-05-10 7:19 ` Andrzej Hajda
2022-05-10 7:50 ` Javier Martinez Canillas
2022-05-11 13:18 ` Daniel Vetter
2022-05-10 8:04 ` Thomas Zimmermann
2022-05-10 8:30 ` Javier Martinez Canillas
2022-05-10 8:37 ` Thomas Zimmermann
2022-05-10 8:50 ` Thomas Zimmermann
2022-05-10 9:06 ` Javier Martinez Canillas
2022-05-10 9:39 ` Thomas Zimmermann
2022-05-10 9:44 ` Javier Martinez Canillas
2022-05-09 18:32 ` Thomas Zimmermann
2022-05-09 20:00 ` Javier Martinez Canillas
2022-05-11 13:15 ` Daniel Vetter
2022-05-05 22:04 ` [PATCH v3 2/4] fbdev: simplefb: Cleanup fb_info in .fb_destroy rather than .remove Javier Martinez Canillas
2022-05-05 22:05 ` [PATCH v3 3/4] fbdev: efifb: " Javier Martinez Canillas
2022-05-06 13:07 ` Andrzej Hajda
2022-05-06 13:18 ` Javier Martinez Canillas
2022-05-08 15:40 ` [fbdev] c6a2b1a999: BUG:KASAN:use-after-free_in_efifb_destroy kernel test robot
2022-05-05 22:06 ` [PATCH v3 4/4] fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove Javier Martinez Canillas
2022-05-06 7:34 ` [PATCH v3 0/4] fbdev: Fix use-after-free caused by wrong fb_info cleanup in drivers Javier Martinez Canillas
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