On Wed, Sep 12, 2018 at 12:30 AM, Tomi Valkeinen tomi.valkeinen@ti.com wrote:

OMAPFB_MEMORY_READ ioctl reads pixels from the LCD's memory and copies them to a userspace buffer. The code has two issues:

• The user provided width and height could be large enough to overflow the calculations
• The copy_to_user() can copy uninitialized memory to the userspace, which might contain sensitive kernel information.

Fix these by limiting the width & height parameters, and only copying the amount of data that we actually received from the LCD.

Signed-off-by: Tomi Valkeinen tomi.valkeinen@ti.com Reported-by: Jann Horn jannh@google.com Cc: stable@vger.kernel.org Cc: security@kernel.org Cc: Will Deacon will.deacon@arm.com Cc: Jann Horn jannh@google.com Cc: Tony Lindgren tony@atomide.com

---

drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c b/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c index ef69273074ba..a3edb20ea4c3 100644 --- a/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c +++ b/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c @@ -496,6 +496,9 @@ static int omapfb_memory_read(struct fb_info *fbi, if (!access_ok(VERIFY_WRITE, mr->buffer, mr->buffer_size)) return -EFAULT;

•   if (mr->w > 4096 || mr->h > 4096)
  

•           return -EINVAL;
  

•   if (mr->w * mr->h * 3 > mr->buffer_size)
            return -EINVAL;
  

alternatively, replace the above two tests with:

alloc_size = array3_size(mr->w, mr->h, 3); if (alloc_size > mr->buffer_size) return -EINVAL;

buf = vmalloc(alloc_size); ...

@@ -509,7 +512,7 @@ static int omapfb_memory_read(struct fb_info *fbi, mr->x, mr->y, mr->w, mr->h);

    if (r > 0) {

•           if (copy_to_user(mr->buffer, buf, mr->buffer_size))
  

•           if (copy_to_user(mr->buffer, buf, r))
  

But yes, this seems correct regardless: userspace was being overwritten beyond "r", potentially.

-Kees

                    r = -EFAULT;
    }

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