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

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[ Upstream commit 666b90b3ce ]

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

Fixes: 27599aacba ("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-javierm@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Javier Martinez Canillas 2022-05-06 00:04:56 +02:00 committed by Greg Kroah-Hartman
parent 4ebbf76dcb
commit 02eef429bf
1 changed files with 7 additions and 1 deletions
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8
drivers/video/fbdev/simplefb.c
View file

@ -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;
}