[PATCH 4.4 34/56] gpio: ml-ioh: Fix buffer underwrite on probe error path

[Greg Kroah-Hartman]

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

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

From: Anton Vasilyev <vasilyev@xxxxxxxxx>

[ Upstream commit 4bf4eed44bfe288f459496eaf38089502ef91a79 ]

If ioh_gpio_probe() fails on devm_irq_alloc_descs() then chip may point
to any element of chip_save array, so reverse iteration from pointer chip
may become chip_save[-1] and gpiochip_remove() will operate with wrong
memory.

The patch fix the error path of ioh_gpio_probe() to correctly bypass
chip_save array.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@xxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpio-ml-ioh.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpio/gpio-ml-ioh.c
+++ b/drivers/gpio/gpio-ml-ioh.c
@@ -495,9 +495,10 @@ err_irq_alloc_descs:
 
 	chip = chip_save;
 err_gpiochip_add:
+	chip = chip_save;
 	while (--i >= 0) {
-		chip--;
 		gpiochip_remove(&chip->gpio);
+		chip++;
 	}
 	kfree(chip_save);