linux-kernel - Re: [PATCH] regulator: core: avoid regulator_resolve

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Message-ID: <20210121154418.GE4588@sirena.org.uk>
Date:   Thu, 21 Jan 2021 15:44:18 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     David Collins <collinsd@...eaurora.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH] regulator: core: avoid regulator_resolve_supply() race
 condition

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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