of/device: Prevent buffer overflow in of_device_modalias()

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>

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 28c38c756f92858906ca2aee54a9c922522f9253..9af44f6dc17b5a64f9cfeb4d71a2d119dab016a7 100644 (file)
--- 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;