Re: [PATCH] gpio: cdev: sanitize the label before requesting the interrupt

On Wed, Mar 20, 2024 at 01:59:44PM +0100, Bartosz Golaszewski wrote:

From: Bartosz Golaszewski bartosz.golaszewski@linaro.org

When an interrupt is requested, a procfs directory is created under "/proc/irq/<irqnum>/<label>" where <label> is the string passed to one of the request_irq() variants.

What follows is that the string must not contain the "/" character or the procfs mkdir operation will fail. We don't have such constraints for GPIO consumer labels which are used verbatim as interrupt labels for GPIO irqs. We must therefore sanitize the consumer string before requesting the interrupt.

As previously mentioned, it would be nice for that constraint to be documented in the irq header to help prevent others falling into the same trap. Else a short comment in the code here to explain the need for sanitization.

Let's replace all "/" with "-".

I actually prefer the ":" you originally suggested, as it more clearly indicates a tier separation, whereas a hyphen is commonly used for multi-word names. And as the hyphen is more commonly used the sanitized name is more likely to conflict.

Cc: stable@vger.kernel.org Reported-by: Stefan Wahren wahrenst@gmx.net Closes: https://lore.kernel.org/linux-gpio/39fe95cb-aa83-4b8b-8cab-63947a726754@gmx.... Signed-off-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org

---

drivers/gpio/gpiolib-cdev.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index f384fa278764..8b5e8e92cbb5 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -1083,10 +1083,20 @@ static u32 gpio_v2_line_config_debounce_period(struct gpio_v2_line_config *lc, return 0; }

+static inline char *make_irq_label(const char *orig) +{

• return kstrdup_and_replace(orig, '/', '-', GFP_KERNEL);

+}

+static inline void free_irq_label(const char *label) +{

• kfree(label);

+}

static void edge_detector_stop(struct line *line) { if (line->irq) {

• free_irq(line->irq, line);
  

• free_irq_label(free_irq(line->irq, line));
  

  line->irq = 0; }

@@ -1110,6 +1120,7 @@ static int edge_detector_setup(struct line *line, unsigned long irqflags = 0; u64 eflags; int irq, ret;

• char *label;

  eflags = edflags & GPIO_V2_LINE_EDGE_FLAGS; if (eflags && !kfifo_initialized(&line->req->events)) {

@@ -1146,11 +1157,17 @@ static int edge_detector_setup(struct line *line, IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING; irqflags |= IRQF_ONESHOT;

• label = make_irq_label(line->req->label);
• if (!label)

• return -ENOMEM;
  

• /* Request a thread to read the events */ ret = request_threaded_irq(irq, edge_irq_handler, edge_irq_thread,

• 		   irqflags, line->req->label, line);
  

• if (ret)

• 		   irqflags, label, line);
  

• if (ret) {

• free_irq_label(label);
  

  return ret;

• }

  line->irq = irq; return 0;

@@ -1973,7 +1990,7 @@ static void lineevent_free(struct lineevent_state *le) blocking_notifier_chain_unregister(&le->gdev->device_notifier, &le->device_unregistered_nb); if (le->irq)

• free_irq(le->irq, le);
  

• free_irq_label(free_irq(le->irq, le));
  

  if (le->desc) gpiod_free(le->desc); kfree(le->label);

@@ -2114,6 +2131,7 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip) int fd; int ret; int irq, irqflags = 0;

• char *label;

  if (copy_from_user(&eventreq, ip, sizeof(eventreq))) return -EFAULT;

@@ -2198,12 +2216,16 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip) if (ret) goto out_free_le;

• label = make_irq_label(le->label);
• if (!label)

• goto out_free_le;
  

Need to set ret = -ENOMEM before the goto, else you will return 0.

Cheers, Kent.

/* Request a thread to read the events */ ret = request_threaded_irq(irq, lineevent_irq_handler, lineevent_irq_thread, irqflags,

• 		   le->label,
  

• 		   label,
  	   le);
  

  if (ret) goto out_free_le;

-- 2.40.1