gpiolib: Fix locking on gpio debugfs files

The debugfs files really need to hold the gpiolib spinlock before
accessing the list. Otherwise chip addition/removal will cause an oops.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5050693dcc35..4b3f388bcc6d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2053,29 +2053,35 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 
 static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
 {
+        unsigned long flags;
         struct gpio_chip *chip = NULL;
         loff_t index = *pos;
 
-        /* REVISIT this isn't locked against gpio_chip removal ... */
-
         s->private = "";
 
+        spin_lock_irqsave(&gpio_lock, flags);
         list_for_each_entry(chip, &gpio_chips, list)
-                if (index-- == 0)
+                if (index-- == 0) {
+                        spin_unlock_irqrestore(&gpio_lock, flags);
                         return chip;
+                }
+        spin_unlock_irqrestore(&gpio_lock, flags);
 
         return NULL;
 }
 
 static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
 {
+        unsigned long flags;
         struct gpio_chip *chip = v;
         void *ret = NULL;
 
+        spin_lock_irqsave(&gpio_lock, flags);
         if (list_is_last(&chip->list, &gpio_chips))
                 ret = NULL;
         else
                 ret = list_entry(chip->list.next, struct gpio_chip, list);
+        spin_unlock_irqrestore(&gpio_lock, flags);
 
         s->private = "\n";
         ++*pos;