Unverified Commit 666b90b3 authored by Javier Martinez Canillas's avatar Javier Martinez Canillas
Browse files

fbdev: simplefb: Cleanup fb_info in .fb_destroy rather than .remove 



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 27599aac ("fbdev: Hot-unplug firmware fb devices on forced removal").

Fixes: 27599aac ("fbdev: Hot-unplug firmware fb devices on forced removal")
Suggested-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Reviewed-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220505220456.366090-1-javierm@redhat.com
parent 89bfd401

drivers/video/fbdev/simplefb.c

+7 −1
Original line number Diff line number Diff line
@@ -84,6 +84,10 @@ 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)

{

	struct simplefb_par *par = info->par;
@@ -94,6 +98,8 @@ static void simplefb_destroy(struct fb_info *info) 
	if (info->screen_base)

		iounmap(info->screen_base);



	framebuffer_release(info);



	if (mem)

		release_mem_region(mem->start, resource_size(mem));

}
@@ -545,8 +551,8 @@ 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;

}