gpio: GPIO_GET_CHIPINFO_IOCTL: Fix line offset validation

The current line offset validation is off by one. Depending on the data
stored behind the descs array this can either cause undefined behavior or
disclose arbitrary, potentially sensitive, memory to the issuing userspace
application.

Make sure that offset is within the bounds of the desc array.

Cc: stable@vger.kernel.org
Fixes: 521a2ad6f862 ("gpio: add userspace ABI for GPIO line information")
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 f0fc3a0d37c829de62e3c136f37cdb7a835a11b7..dac975397253d5cbfae19652ef2fb3a82a84c54e 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -839,7 +839,7 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 
                if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
                        return -EFAULT;
-               if (lineinfo.line_offset > gdev->ngpio)
+               if (lineinfo.line_offset >= gdev->ngpio)
                        return -EINVAL;
 
                desc = &gdev->descs[lineinfo.line_offset];