From: Javier Martinez Canillas javierm@redhat.com
[ Upstream commit 666b90b3ce9e4aac1e1deba266c3a230fb3913b0 ]
The driver is calling framebuffer_release() in its .remove callback, but this will cause the struct fb_info to be freed too early. Since it could be that a reference is still hold to it if user-space opened the fbdev.
This would lead to a use-after-free error if the framebuffer device was unregistered but later a user-space process tries to close the fbdev fd.
To prevent this, move the framebuffer_release() call to fb_ops.fb_destroy instead of doing it in the driver's .remove callback.
Strictly speaking, the code flow in the driver is still wrong because all the hardware cleanupd (i.e: iounmap) should be done in .remove while the software cleanup (i.e: releasing the framebuffer) should be done in the .fb_destroy handler. But this at least makes to match the behavior before commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal").
Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal") Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Link: https://patchwork.freedesktop.org/patch/msgid/20220505220456.366090-1-javier... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/simplefb.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c index b63074fd892e..a2e3a4690025 100644 --- a/drivers/video/fbdev/simplefb.c +++ b/drivers/video/fbdev/simplefb.c @@ -70,12 +70,18 @@ struct simplefb_par; static void simplefb_clocks_destroy(struct simplefb_par *par); static void simplefb_regulators_destroy(struct simplefb_par *par);
+/* + * fb_ops.fb_destroy is called by the last put_fb_info() call at the end + * of unregister_framebuffer() or fb_release(). Do any cleanup here. + */ static void simplefb_destroy(struct fb_info *info) { simplefb_regulators_destroy(info->par); simplefb_clocks_destroy(info->par); if (info->screen_base) iounmap(info->screen_base); + + framebuffer_release(info); }
static const struct fb_ops simplefb_ops = { @@ -520,8 +526,8 @@ static int simplefb_remove(struct platform_device *pdev) { struct fb_info *info = platform_get_drvdata(pdev);
+ /* simplefb_destroy takes care of info cleanup */ unregister_framebuffer(info); - framebuffer_release(info);
return 0; }