fbdev/omapfb: fix omapfb_memory_read infoleak

Message ID 20180912073046.26475-1-tomi.valkeinen@ti.com
State New
Headers show
Series
  • fbdev/omapfb: fix omapfb_memory_read infoleak
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Commit Message

Tomi Valkeinen Sept. 12, 2018, 7:30 a.m.
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(-)

-- 
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Comments

Kees Cook Sept. 12, 2018, 5:32 p.m. | #1
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;

>         }

>

> --

> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.

> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

>




-- 
Kees Cook
Pixel Security
Bartlomiej Zolnierkiewicz Sept. 26, 2018, 3:45 p.m. | #2
[ added dri-devel@lists.freedesktop.org to Cc: ]

On 09/12/2018 09:30 AM, Tomi Valkeinen 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>


Patch queued for 4.19, thanks.

> ---

>  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;

>  

> @@ -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))

>  			r = -EFAULT;

>  	}


Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Patch

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;
 
@@ -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))
 			r = -EFAULT;
 	}