pinctrl: avoid unsafe code pattern in find_pinctrl()

commit c153a4edff6ab01370fcac8e46f9c89cca1060c2 upstream.

The code in find_pinctrl() takes a mutex and traverses a list of pinctrl
structures. Later the caller bumps up reference count on the found
structure. Such pattern is not safe as pinctrl that was found may get
deleted before the caller gets around to increasing the reference count.

Fix this by taking the reference count in find_pinctrl(), while it still
holds the mutex.

Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/ZQs1RgTKg6VJqmPs@google.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 83f439906d3168dee10b5aa0ee3d2972bfa09f51..f17514f237a50c822356f0fa8c069242e2148923 100644 (file)
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -973,17 +973,20 @@ static int add_setting(struct pinctrl *p, struct pinctrl_dev *pctldev,
 
 static struct pinctrl *find_pinctrl(struct device *dev)
 {
-       struct pinctrl *p;
+       struct pinctrl *entry, *p = NULL;
 
        mutex_lock(&pinctrl_list_mutex);
-       list_for_each_entry(p, &pinctrl_list, node)
-               if (p->dev == dev) {
-                       mutex_unlock(&pinctrl_list_mutex);
-                       return p;
+
+       list_for_each_entry(entry, &pinctrl_list, node) {
+               if (entry->dev == dev) {
+                       p = entry;
+                       kref_get(&p->users);
+                       break;
                }
+       }
 
        mutex_unlock(&pinctrl_list_mutex);
-       return NULL;
+       return p;
 }
 
 static void pinctrl_free(struct pinctrl *p, bool inlist);
@@ -1092,7 +1095,6 @@ struct pinctrl *pinctrl_get(struct device *dev)
        p = find_pinctrl(dev);
        if (p) {
                dev_dbg(dev, "obtain a copy of previously claimed pinctrl\n");
-               kref_get(&p->users);
                return p;
        }