[PATCH] fbdev/omapfb: fix omapfb_memory_read infoleak

Subsystems: framebuffer layer, omap display subsystem and framebuffer support (dss2), the rest

STALE2941d

3 messages, 3 authors, 2018-09-26 · open the first message on its own page

[PATCH] fbdev/omapfb: fix omapfb_memory_read infoleak

From: Tomi Valkeinen <hidden>
Date: 2018-09-12 12:34:50

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 <redacted>
Reported-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Cc: security@kernel.org
Cc: Will Deacon <redacted>
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;

@@ -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;
 	}

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

Re: [PATCH] fbdev/omapfb: fix omapfb_memory_read infoleak

From: Kees Cook <hidden>
Date: 2018-09-12 22:38:30

On Wed, Sep 12, 2018 at 12:30 AM, Tomi Valkeinen [off-list ref] wrote:

quoted hunk

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 <redacted>
Reported-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Cc: security@kernel.org
Cc: Will Deacon <redacted>
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);
...

quoted hunk

@@ -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

Re: [PATCH] fbdev/omapfb: fix omapfb_memory_read infoleak

From: Bartlomiej Zolnierkiewicz <hidden>
Date: 2018-09-26 21:59:29

[ 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 <redacted>
Reported-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Cc: security@kernel.org
Cc: Will Deacon <redacted>
Cc: Jann Horn <jannh@google.com>
Cc: Tony Lindgren <tony@atomide.com>

Patch queued for 4.19, thanks.

quoted hunk

---
 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

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