Re: [PATCH] video: fbdev: imxfb: use after free in imxfb_remove()

[Dan Carpenter <dan.carpenter@oracle.com>]

On Tue, Jul 04, 2017 at 05:44:57PM +0200, Bartlomiej Zolnierkiewicz wrote:
> 
> Hi,
> 
> On Friday, June 30, 2017 11:02:42 AM Dan Carpenter wrote:
> > We free "info" then dereference it on the next line.  I've moved the
> > call to framebuffer_release() down a line to avoid this problem.
> > 
> > Fixes: b7d2d37276c1 ("video: imxfb: Remove unused fields from platform data structure")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > 
> > diff --git a/drivers/video/fbdev/imxfb.c b/drivers/video/fbdev/imxfb.c
> > index c166e0725be5..1d0c3592b290 100644
> > --- a/drivers/video/fbdev/imxfb.c
> > +++ b/drivers/video/fbdev/imxfb.c
> > @@ -1080,10 +1080,9 @@ static int imxfb_remove(struct platform_device *pdev)
> >  
> >  	fb_dealloc_cmap(&info->cmap);
> >  	kfree(info->pseudo_palette);
> > -	framebuffer_release(info);
> > -
> >  	dma_free_wc(&pdev->dev, fbi->map_size, info->screen_base,
> >  		    fbi->map_dma);
> > +	framebuffer_release(info);
> >  
> >  	iounmap(fbi->regs);
> 
> Good catch.
> 
> While you are at it, please:
> 
> - move framebuffer_release() after iounmap() (memory occupied by
>   fbi will also be freed by framebuffer_release() call, please see
>   framebuffer_alloc() for details)
> 

I'm still recovering from an illness so I might not be thinking
straight.  I don't see a bug here.  But I agree that it should mirror
the probe function so I'll re-write the patch.

regards,
dan carpenter