Re: [PATCH] regulator: core: avoid regulator_resolve_supply() race condition

[Mark Brown]

On Thu, Jan 21, 2021 at 10:41:59AM +0100, Marek Szyprowski wrote:
> On 18.01.2021 21:49, Mark Brown wrote:

> > Does this help (completely untested):

> Sadly nope. I get same warning:

Try this instead:

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3ae5ccd9277d..31503776dbd7 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1823,17 +1823,6 @@ static int regulator_resolve_supply(struct regulator_dev 
*rdev)
        if (rdev->supply)
                return 0;
 
-       /*
-        * Recheck rdev->supply with rdev->mutex lock held to avoid a race
-        * between rdev->supply null check and setting rdev->supply in
-        * set_supply() from concurrent tasks.
-        */
-       regulator_lock(rdev);
-
-       /* Supply just resolved by a concurrent task? */
-       if (rdev->supply)
-               goto out;
-
        r = regulator_dev_lookup(dev, rdev->supply_name);
        if (IS_ERR(r)) {
                ret = PTR_ERR(r);
@@ -1885,12 +1874,29 @@ static int regulator_resolve_supply(struct 
regulator_dev *rdev)
                goto out;
        }
 
+       /*
+        * Recheck rdev->supply with rdev->mutex lock held to avoid a race
+        * between rdev->supply null check and setting rdev->supply in
+        * set_supply() from concurrent tasks.
+        */
+       regulator_lock(rdev);
+
+       /* Supply just resolved by a concurrent task? */
+       if (rdev->supply) {
+               regulator_unlock(rdev);
+               put_device(&r->dev);
+               return ret;
+       }
+
        ret = set_supply(rdev, r);
        if (ret < 0) {
+               regulator_unlock(rdev);
                put_device(&r->dev);
-               goto out;
+               return ret;
        }
 
+       regulator_unlock(rdev);
+
        /*
         * In set_machine_constraints() we may have turned this regulator on
         * but we couldn't propagate to the supply if it hadn't been resolved
@@ -1901,12 +1907,11 @@ static int regulator_resolve_supply(struct 
regulator_dev *rdev)
                if (ret < 0) {
                        _regulator_put(rdev->supply);
                        rdev->supply = NULL;
-                       goto out;
+                       goto out_rdev_lock;
                }
        }
 
 out:
-       regulator_unlock(rdev);
        return ret;
 }
 

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