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fbdev/omapfb: fix omapfb_memory_read infoleak

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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>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
This commit is contained in:
Tomi Valkeinen 2018-09-26 18:11:22 +02:00 committed by Bartlomiej Zolnierkiewicz
parent d85536cde9
commit 1bafcbf59f
1 changed files with 4 additions and 1 deletions
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5
drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c
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@ -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;
}