Re: [PATCH 1/2] gpio: cdev: fix missed label sanitizing in debounce_setup()

On Wed, Apr 3, 2024 at 3:15 PM Kent Gibson warthog618@gmail.com wrote:

When adding sanitization of the label, the path through edge_detector_setup() that leads to debounce_setup() was overlooked. A request taking this path does not allocate a new label and the request label is freed twice when the request is released, resulting in memory corruption.

Add label sanitization to debounce_setup().

Cc: stable@vger.kernel.org Fixes: b34490879baa ("gpio: cdev: sanitize the label before requesting the interrupt") Signed-off-by: Kent Gibson warthog618@gmail.com

---

drivers/gpio/gpiolib-cdev.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index fa9635610251..f4c2da2041e5 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -728,6 +728,16 @@ static u32 line_event_id(int level) GPIO_V2_LINE_EVENT_FALLING_EDGE; }

+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);
  

+}

#ifdef CONFIG_HTE

static enum hte_return process_hw_ts_thread(void *p) @@ -1015,6 +1025,7 @@ static int debounce_setup(struct line *line, unsigned int debounce_period_us) { unsigned long irqflags; int ret, level, irq;

•   char *label;
  
    /* try hardware */
    ret = gpiod_set_debounce(line->desc, debounce_period_us);
  

@@ -1037,11 +1048,17 @@ static int debounce_setup(struct line *line, unsigned int debounce_period_us) if (irq < 0) return -ENXIO;

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

Now that I look at the actual patch, I don't really like it. We introduce a bug just to fix it a commit later. Such things have been frowned upon in the past.

Let me shuffle the code a bit, I'll try to make it a bit more correct.

Bart

•                   if (!label)
  

•                           return -ENOMEM;
  

•                   irqflags = IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
                    ret = request_irq(irq, debounce_irq_handler, irqflags,
  

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

•                   if (ret)
  

•                                     label, line);
  

•                   if (ret) {
  

•                           free_irq_label(label);
                            return ret;
  

•                   }
                    line->irq = irq;
            } else {
                    ret = hte_edge_setup(line, GPIO_V2_LINE_FLAG_EDGE_BOTH);
  

@@ -1083,16 +1100,6 @@ 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) { -- 2.39.2