pinctrl: check the return value of pinmux_ops::get_function_name()

While the API contract in docs doesn't specify it explicitly, the
generic implementation of the get_function_name() callback from struct
pinmux_ops - pinmux_generic_get_function_name() - can fail and return
NULL. This is already checked in pinmux_check_ops() so add a similar
check in pinmux_func_name_to_selector() instead of passing the returned
pointer right down to strcmp() where the NULL can get dereferenced. This
is normal operation when adding new pinfunctions.

Cc: stable@vger.kernel.org
Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 79814758a084570adea0ea1a3151d186f65d1d1f..07a478b2c48740c24a32e6ac8f10df4876e718e3 100644 (file)
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -337,7 +337,7 @@ static int pinmux_func_name_to_selector(struct pinctrl_dev *pctldev,
        while (selector < nfuncs) {
                const char *fname = ops->get_function_name(pctldev, selector);
 
-               if (!strcmp(function, fname))
+               if (fname && !strcmp(function, fname))
                        return selector;
 
                selector++;