linux-kernel - [PATCH] drivers/usb/serial/mos*: prevent reading uninitialized stack memory

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Date:	Wed, 15 Sep 2010 17:44:16 -0400
From:	Dan Rosenberg <drosenberg@...curity.com>
To:	linux-usb@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, security@...nel.org,
	stable@...nel.org
Subject: [PATCH] drivers/usb/serial/mos*: prevent reading uninitialized
 stack memory

The TIOCGICOUNT device ioctl in both mos7720.c and mos7840.c allows
unprivileged users to read uninitialized stack memory, because the
"reserved" member of the serial_icounter_struct struct declared on the
stack is not altered or zeroed before being copied back to the user.
This patch takes care of it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>

diff -urp linux-2.6.35.4.orig/drivers/usb/serial/mos7720.c linux-2.6.35.4/drivers/usb/serial/mos7720.c
--- linux-2.6.35.4.orig/drivers/usb/serial/mos7720.c	2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/usb/serial/mos7720.c	2010-09-15 11:42:01.877375361 -0400
@@ -2024,6 +2024,9 @@ static int mos7720_ioctl(struct tty_stru
 
 	case TIOCGICOUNT:
 		cnow = mos7720_port->icount;
+
+		memset(&icount, 0, sizeof(struct serial_icounter_struct));
+
 		icount.cts = cnow.cts;
 		icount.dsr = cnow.dsr;
 		icount.rng = cnow.rng;
diff -urp linux-2.6.35.4.orig/drivers/usb/serial/mos7840.c linux-2.6.35.4/drivers/usb/serial/mos7840.c
--- linux-2.6.35.4.orig/drivers/usb/serial/mos7840.c	2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/usb/serial/mos7840.c	2010-09-15 11:42:39.237375173 -0400
@@ -2273,6 +2273,9 @@ static int mos7840_ioctl(struct tty_stru
 	case TIOCGICOUNT:
 		cnow = mos7840_port->icount;
 		smp_rmb();
+
+		memset(&icount, 0, sizeof(struct serial_icounter_struct));
+
 		icount.cts = cnow.cts;
 		icount.dsr = cnow.dsr;
 		icount.rng = cnow.rng;






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