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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Jann Horn" <jannh@google.com>,
        "Tony Lindgren" <tony@atomide.com>, security@kernel.org,
        "Will Deacon" <will.deacon@arm.com>,
        "Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
        "Tomi Valkeinen" <tomi.valkeinen@ti.com>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.674270191@decadent.org.uk>
Subject: [PATCH 3.16 264/328] fbdev/omapfb: fix omapfb_memory_read infoleak
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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;
 	}