linux-kernel - [PATCH AUTOSEL 4.14 083/115] fbdev: sbuslib: integer overflow in sbusfb_ioctl

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Date:   Tue, 12 Nov 2019 20:55:50 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Peter Malone <peter.malone@...il.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 083/115] fbdev: sbuslib: integer overflow in sbusfb_ioctl_helper()

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit e5017716adb8aa5c01c52386c1b7470101ffe9c5 ]

The "index + count" addition can overflow.  Both come directly from the
user.  This bug leads to an information leak.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Peter Malone <peter.malone@...il.com>
Cc: Philippe Ombredanne <pombredanne@...b.com>
Cc: Mathieu Malaterre <malat@...ian.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/video/fbdev/sbuslib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
index 90c51330969c2..01a7110e61a76 100644
--- a/drivers/video/fbdev/sbuslib.c
+++ b/drivers/video/fbdev/sbuslib.c
@@ -171,7 +171,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		    get_user(ublue, &c->blue))
 			return -EFAULT;
 
-		if (index + count > cmap->len)
+		if (index > cmap->len || count > cmap->len - index)
 			return -EINVAL;
 
 		for (i = 0; i < count; i++) {
-- 
2.20.1