gpio: GPIOHANDLE_GET_LINE_VALUES_IOCTL: Fix information leak

The GPIOHANDLE_GET_LINE_VALUES_IOCTL handler allocates a gpiohandle_data
struct on the stack and then passes it to copy_to_user(). But only the
first element of the values array in the struct is set, which leaves the
struct partially initialized.

This exposes the previous, potentially sensitive, stack content to the
issuing userspace application. To avoid this make sure that the struct is
fully initialized.

Cc: stable@vger.kernel.org
Fixes: 61f922db7221 ("gpio: userspace ABI for reading GPIO line events")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d287cb4e97c4bac4faedf152affd30a85b4b31ce..4ed26bcf054c5c419ecb524523fc0b64d6a82230 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -628,6 +628,8 @@ static long lineevent_ioctl(struct file *filep, unsigned int cmd,
        if (cmd == GPIOHANDLE_GET_LINE_VALUES_IOCTL) {
                int val;
 
+               memset(&ghd, 0, sizeof(ghd));
+
                val = gpiod_get_value_cansleep(le->desc);
                if (val < 0)
                        return val;