linux-kernel - [PATCH 3.12 019/111] usb: chipidea: debug: avoid out of bound read

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Message-Id: <fb6af6cb768a33df9ecc7ace4481da155396bd04.1433943052.git.jslaby@suse.cz>
Date:	Wed, 10 Jun 2015 17:26:08 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Heinrich Schuchardt <xypron.glpk@....de>,
	Peter Chen <peter.chen@...escale.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 019/111] usb: chipidea: debug: avoid out of bound read

From: Heinrich Schuchardt <xypron.glpk@....de>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit bd5fb0aec3dd7cde7ec4c397b10e55d4c9626d8d upstream.

A string written by the user may not be zero terminated.

sscanf may read memory beyond the buffer if no zero byte
is found.

For testing build with CONFIG_USB_CHIPIDEA=y, CONFIG_USB_CHIPIDEA_DEBUG=y.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
Signed-off-by: Peter Chen <peter.chen@...escale.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/usb/chipidea/debug.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
index 96d899aee473..92f0cc442d46 100644
--- a/drivers/usb/chipidea/debug.c
+++ b/drivers/usb/chipidea/debug.c
@@ -84,9 +84,13 @@ static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf,
 	char buf[32];
 	int ret;
 
-	if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
+	count = min_t(size_t, sizeof(buf) - 1, count);
+	if (copy_from_user(buf, ubuf, count))
 		return -EFAULT;
 
+	/* sscanf requires a zero terminated string */
+	buf[count] = '\0';
+
 	if (sscanf(buf, "%u", &mode) != 1)
 		return -EINVAL;
 
-- 
2.4.2

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