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regulator: core: avoid regulator_resolve_supply() race condition
The final step in regulator_register() is to call regulator_resolve_supply() for each registered regulator (including the one in the process of being registered). The regulator_resolve_supply() function first checks if rdev->supply is NULL, then it performs various steps to try to find the supply. If successful, rdev->supply is set inside of set_supply(). This procedure can encounter a race condition if two concurrent tasks call regulator_register() near to each other on separate CPUs and one of the regulators has rdev->supply_name specified. There is currently nothing guaranteeing atomicity between the rdev->supply check and set steps. Thus, both tasks can observe rdev->supply==NULL in their regulator_resolve_supply() calls. This then results in both creating a struct regulator for the supply. One ends up actually stored in rdev->supply and the other is lost (though still present in the supply's consumer_list). Here is a kernel log snippet showing the issue: [ 12.421768] gpu_cc_gx_gdsc: supplied by pm8350_s5_level [ 12.425854] gpu_cc_gx_gdsc: supplied by pm8350_s5_level [ 12.429064] debugfs: Directory 'regulator.4-SUPPLY' with parent '17a00000.rsc:rpmh-regulator-gfxlvl-pm8350_s5_level' already present! Avoid this race condition by holding the rdev->mutex lock inside of regulator_resolve_supply() while checking and setting rdev->supply. Signed-off-by: David Collins <collinsd@codeaurora.org> Link: https://lore.kernel.org/r/1610068562-4410-1-git-send-email-collinsd@codeaurora.org Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
parent
36836f5b37
commit
eaa7995c52
1 changed files with 28 additions and 11 deletions
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@ -1813,23 +1813,34 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
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{
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struct regulator_dev *r;
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struct device *dev = rdev->dev.parent;
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int ret;
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int ret = 0;
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/* No supply to resolve? */
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if (!rdev->supply_name)
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return 0;
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/* Supply already resolved? */
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/* Supply already resolved? (fast-path without locking contention) */
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if (rdev->supply)
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return 0;
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/*
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* Recheck rdev->supply with rdev->mutex lock held to avoid a race
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* between rdev->supply null check and setting rdev->supply in
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* set_supply() from concurrent tasks.
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*/
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regulator_lock(rdev);
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/* Supply just resolved by a concurrent task? */
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if (rdev->supply)
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goto out;
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r = regulator_dev_lookup(dev, rdev->supply_name);
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if (IS_ERR(r)) {
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ret = PTR_ERR(r);
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/* Did the lookup explicitly defer for us? */
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if (ret == -EPROBE_DEFER)
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return ret;
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goto out;
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if (have_full_constraints()) {
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r = dummy_regulator_rdev;
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@ -1837,15 +1848,18 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
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} else {
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dev_err(dev, "Failed to resolve %s-supply for %s\n",
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rdev->supply_name, rdev->desc->name);
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return -EPROBE_DEFER;
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ret = -EPROBE_DEFER;
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goto out;
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}
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}
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if (r == rdev) {
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dev_err(dev, "Supply for %s (%s) resolved to itself\n",
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rdev->desc->name, rdev->supply_name);
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if (!have_full_constraints())
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return -EINVAL;
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if (!have_full_constraints()) {
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ret = -EINVAL;
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goto out;
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}
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r = dummy_regulator_rdev;
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get_device(&r->dev);
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}
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@ -1859,7 +1873,8 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
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if (r->dev.parent && r->dev.parent != rdev->dev.parent) {
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if (!device_is_bound(r->dev.parent)) {
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put_device(&r->dev);
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return -EPROBE_DEFER;
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ret = -EPROBE_DEFER;
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goto out;
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}
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}
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@ -1867,13 +1882,13 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
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ret = regulator_resolve_supply(r);
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if (ret < 0) {
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put_device(&r->dev);
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return ret;
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goto out;
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}
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ret = set_supply(rdev, r);
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if (ret < 0) {
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put_device(&r->dev);
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return ret;
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goto out;
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}
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/*
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@ -1886,11 +1901,13 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
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if (ret < 0) {
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_regulator_put(rdev->supply);
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rdev->supply = NULL;
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return ret;
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goto out;
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}
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}
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return 0;
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out:
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regulator_unlock(rdev);
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return ret;
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}
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/* Internal regulator request function */
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