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 depending on
the number of requested line handles the struct is only 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: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
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 db44a7da5eb44cec137d956175eea6dd7c33bef1..7f92f8964efdd5ec6b037ad3ddc3b8af47ba6c56 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -344,6 +344,8 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd,
        if (cmd == GPIOHANDLE_GET_LINE_VALUES_IOCTL) {
                int val;
 
+               memset(&ghd, 0, sizeof(ghd));
+
                /* TODO: check if descriptors are really input */
                for (i = 0; i < lh->numdescs; i++) {
                        val = gpiod_get_value_cansleep(lh->descs[i]);