[PATCH 3.16 264/328] fbdev/omapfb: fix omapfb_memory_read infoleak

Ben Hutchings
2018-12-09T22:00:40Z

From: Tomi Valkeinen <tomi.valkeinen@ti.com>

commit 1bafcbf59fed92af58955024452f45430d3898c5 upstream.

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: security@kernel.org
Cc: Will Deacon <will.deacon@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c
+++ b/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c
@@ -493,6 +493,9 @@ static int omapfb_memory_read(struct fb_
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;

@@ -506,7 +509,7 @@ static int omapfb_memory_read(struct fb_
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;
}