From: Bjorn Andersson <bjorn.andersson@linaro.org>
Date: Wed, 23 Aug 2017 18:04:04 -0700
Subject: [PATCH] of/device: Prevent buffer overflow in of_device_modalias()
References: bnc#1060662
Patch-mainline: v4.12.12
Git-commit: 08ab58d9de3eb8498ae0585001d0975e46217a39

commit 08ab58d9de3eb8498ae0585001d0975e46217a39 upstream.

As of_device_get_modalias() returns the number of bytes that would have
been written to the target string, regardless of how much did fit in the
buffer, it's possible that the returned index points beyond the buffer
passed to of_device_modalias() - causing memory beyond the buffer to be
null terminated.

Fixes: 0634c2958927 ("of: Add function for generating a DT modalias with a newline")
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/of/device.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 28c38c756f92..9af44f6dc17b 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -274,6 +274,8 @@ ssize_t of_device_modalias(struct device *dev, char *str, ssize_t len)
 	ssize_t sl = of_device_get_modalias(dev, str, len - 2);
 	if (sl < 0)
 		return sl;
+	if (sl > len - 2)
+		return -ENOMEM;
 
 	str[sl++] = '\n';
 	str[sl] = 0;
-- 
2.14.2