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    Subject[PATCH 4.12 41/43] of/device: Prevent buffer overflow in of_device_modalias()
    Date
    4.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Bjorn Andersson <bjorn.andersson@linaro.org>

    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>

    ---
    drivers/of/device.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/of/device.c
    +++ b/drivers/of/device.c
    @@ -274,6 +274,8 @@ ssize_t of_device_modalias(struct device
    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;

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