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    Subject[PATCH 1/4] leds: netdev trigger: use memcpy in device_name_store
    Date
    If userspace doesn't end the input with a newline (which can easily
    happen if the write happens from a C program that does write(fd,
    iface, strlen(iface))), we may end up including garbage from a
    previous, longer value in the device_name. For example

    # cat device_name

    # printf 'eth12' > device_name
    # cat device_name
    eth12
    # printf 'eth3' > device_name
    # cat device_name
    eth32

    I highly doubt anybody is relying on this behaviour, so switch to
    simply copying the bytes (we've already checked that size is <
    IFNAMSIZ) and unconditionally zero-terminate it; of course, we also
    still have to strip a trailing newline.

    This is also preparation for future patches.

    Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
    ---
    drivers/leds/trigger/ledtrig-netdev.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
    index 3dd3ed46d473..ddc2b90ad7ec 100644
    --- a/drivers/leds/trigger/ledtrig-netdev.c
    +++ b/drivers/leds/trigger/ledtrig-netdev.c
    @@ -122,7 +122,8 @@ static ssize_t device_name_store(struct device *dev,
    trigger_data->net_dev = NULL;
    }

    - strncpy(trigger_data->device_name, buf, size);
    + memcpy(trigger_data->device_name, buf, size);
    + trigger_data->device_name[size] = '\0';
    if (size > 0 && trigger_data->device_name[size - 1] == '\n')
    trigger_data->device_name[size - 1] = 0;

    --
    2.20.1
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