[PATCH 2/2] gpio: cdev: check for NULL labels when sanitizing them for irqs

[Kent Gibson <warthog618@xxxxxxxxx>]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

We need to take into account that a line's consumer label may be NULL
and not try to kstrdup() it in that case but rather pass the NULL
pointer up the stack to the interrupt request function.

To that end: let make_irq_label() return NULL as a valid return value
and use ERR_PTR() instead to signal an allocation failure to callers.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: b34490879baa ("gpio: cdev: sanitize the label before requesting the interrupt")
Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/20240402093534.212283-1-naresh.kamboju@xxxxxxxxxx/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
Signed-off-by: Kent Gibson <warthog618@xxxxxxxxx> (rebased)
---
 drivers/gpio/gpiolib-cdev.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index f4c2da2041e5..8112ec36e55f 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -730,7 +730,16 @@ static u32 line_event_id(int level)
 
 static inline char *make_irq_label(const char *orig)
 {
-	return kstrdup_and_replace(orig, '/', ':', GFP_KERNEL);
+	char *new;
+
+	if (!orig)
+		return NULL;
+
+	new = kstrdup_and_replace(orig, '/', ':', GFP_KERNEL);
+	if (!new)
+		return ERR_PTR(-ENOMEM);
+
+	return new;
 }
 
 static inline void free_irq_label(const char *label)
@@ -1049,8 +1058,8 @@ static int debounce_setup(struct line *line, unsigned int debounce_period_us)
 				return -ENXIO;
 
 			label = make_irq_label(line->req->label);
-			if (!label)
-				return -ENOMEM;
+			if (IS_ERR(label))
+				return PTR_ERR(label);
 
 			irqflags = IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
 			ret = request_irq(irq, debounce_irq_handler, irqflags,
@@ -1165,8 +1174,8 @@ static int edge_detector_setup(struct line *line,
 	irqflags |= IRQF_ONESHOT;
 
 	label = make_irq_label(line->req->label);
-	if (!label)
-		return -ENOMEM;
+	if (IS_ERR(label))
+		return PTR_ERR(label);
 
 	/* Request a thread to read the events */
 	ret = request_threaded_irq(irq, edge_irq_handler, edge_irq_thread,
@@ -2224,8 +2233,8 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 		goto out_free_le;
 
 	label = make_irq_label(le->label);
-	if (!label) {
-		ret = -ENOMEM;
+	if (IS_ERR(label)) {
+		ret = PTR_ERR(label);
 		goto out_free_le;
 	}
 
-- 
2.39.2