| Message ID | 20220504215806.57147-1-javierm@redhat.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | fbdev: Fix use-after-free caused by wrong fb_info cleanup in drivers | expand |
Am 04.05.22 um 23:58 schrieb Javier Martinez Canillas: > 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. > > The correct thing to do is to only unregister the framebuffer in the > driver's .remove callback, but do any cleanup in the fb_ops.fb_destroy. > > Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch> > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > --- > > drivers/video/fbdev/efifb.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c > index ea42ba6445b2..cfa3dc0b4eee 100644 > --- a/drivers/video/fbdev/efifb.c > +++ b/drivers/video/fbdev/efifb.c > @@ -243,6 +243,10 @@ static void efifb_show_boot_graphics(struct fb_info *info) > static inline void efifb_show_boot_graphics(struct fb_info *info) {} > #endif > > +/* > + * 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 efifb_destroy(struct fb_info *info) > { > if (efifb_pci_dev) > @@ -254,6 +258,9 @@ static void efifb_destroy(struct fb_info *info) > else > memunmap(info->screen_base); > } > + > + framebuffer_release(info); > + > if (request_mem_succeeded) > release_mem_region(info->apertures->ranges[0].base, > info->apertures->ranges[0].size); > @@ -620,9 +627,9 @@ static int efifb_remove(struct platform_device *pdev) > { > struct fb_info *info = platform_get_drvdata(pdev); > > + /* efifb_destroy takes care of info cleanup */ > unregister_framebuffer(info); > sysfs_remove_groups(&pdev->dev.kobj, efifb_groups); > - framebuffer_release(info); > > return 0; > }
diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c index ea42ba6445b2..cfa3dc0b4eee 100644 --- a/drivers/video/fbdev/efifb.c +++ b/drivers/video/fbdev/efifb.c @@ -243,6 +243,10 @@ static void efifb_show_boot_graphics(struct fb_info *info) static inline void efifb_show_boot_graphics(struct fb_info *info) {} #endif +/* + * 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 efifb_destroy(struct fb_info *info) { if (efifb_pci_dev) @@ -254,6 +258,9 @@ static void efifb_destroy(struct fb_info *info) else memunmap(info->screen_base); } + + framebuffer_release(info); + if (request_mem_succeeded) release_mem_region(info->apertures->ranges[0].base, info->apertures->ranges[0].size); @@ -620,9 +627,9 @@ static int efifb_remove(struct platform_device *pdev) { struct fb_info *info = platform_get_drvdata(pdev); + /* efifb_destroy takes care of info cleanup */ unregister_framebuffer(info); sysfs_remove_groups(&pdev->dev.kobj, efifb_groups); - framebuffer_release(info); return 0; }
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. The correct thing to do is to only unregister the framebuffer in the driver's .remove callback, but do any cleanup in the fb_ops.fb_destroy. Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> --- drivers/video/fbdev/efifb.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)