[PATCH 4.9 092/119] powerpc/sysdev/simple_gpio: Fix oops in gpio save_regs function

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.leroy@xxxxxx>

commit 6f553912eedafae13ff20b322a65e471fe7f5236 upstream.

of_mm_gpiochip_add_data() generates an oops for NULL pointer dereference.

of_mm_gpiochip_add_data() calls mm_gc->save_regs() before
setting the data, therefore ->save_regs() cannot use gpiochip_get_data()

Fixes: 937daafca774 ("powerpc: simple-gpio: use gpiochip data pointer")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/sysdev/simple_gpio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/powerpc/sysdev/simple_gpio.c
+++ b/arch/powerpc/sysdev/simple_gpio.c
@@ -75,7 +75,8 @@ static int u8_gpio_dir_out(struct gpio_c
 
 static void u8_gpio_save_regs(struct of_mm_gpio_chip *mm_gc)
 {
-	struct u8_gpio_chip *u8_gc = gpiochip_get_data(&mm_gc->gc);
+	struct u8_gpio_chip *u8_gc =
+		container_of(mm_gc, struct u8_gpio_chip, mm_gc);
 
 	u8_gc->data = in_8(mm_gc->regs);
 }