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| author |   Javier Martinez Canillas <javierm@redhat.com> | 2022-05-06 00:04:56 +0200 |
|---|---|---|
| committer | Javier Martinez Canillas <javierm@redhat.com> | 2022-05-06 09:21:21 +0200 |
| commit | 666b90b3ce9e4aac1e1deba266c3a230fb3913b0 (patch) | |
| tree | fc84517f97ce38dda7a1ad0548459a18b619da8e | |
| parent | fbdev: Prevent possible use-after-free in fb_release() (diff) | |
| download | linux-dev-666b90b3ce9e4aac1e1deba266c3a230fb3913b0.tar.xz linux-dev-666b90b3ce9e4aac1e1deba266c3a230fb3913b0.zip | |
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 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-javierm@redhat.com
| -rw-r--r-- | drivers/video/fbdev/simplefb.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c index 94fc9c6d0411..2c198561c338 100644 --- a/drivers/video/fbdev/simplefb.c +++ b/drivers/video/fbdev/simplefb.c @@ -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; } |