Re: [PATCH] regulator: fix memory leak on error path of regulator_register()

Re: [PATCH] regulator: fix memory leak on error path of regulator_register()

[Markus Elfring]

> … introduced as a side ef another …

Would the following wording variant be more appropriate?

  … introduced as a side effect of another …


How do you think about to replace the wording “…, I believe …”
by an imperative description?

Regards,
Markus

[PATCH] regulator: fix memory leak on error path of regulator_register()

[Vladimir Zapolskiy]

The change corrects registration and deregistration on error path
of a regulator, the problem was manifested by a reported memory
leak on deferred probe:

    as3722-regulator as3722-regulator: regulator 13 register failed -517

    # cat /sys/kernel/debug/kmemleak
    unreferenced object 0xecc43740 (size 64):
      comm "swapper/0", pid 1, jiffies 4294937640 (age 712.880s)
      hex dump (first 32 bytes):
        72 65 67 75 6c 61 74 6f 72 2e 32 34 00 5a 5a 5a  regulator.24.ZZZ
        5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
      backtrace:
        [<0c4c3d1c>] __kmalloc_track_caller+0x15c/0x2c0
        [<40c0ad48>] kvasprintf+0x64/0xd4
        [<109abd29>] kvasprintf_const+0x70/0x84
        [<c4215946>] kobject_set_name_vargs+0x34/0xa8
        [<62282ea2>] dev_set_name+0x40/0x64
        [<a39b6757>] regulator_register+0x3a4/0x1344
        [<16a9543f>] devm_regulator_register+0x4c/0x84
        [<51a4c6a1>] as3722_regulator_probe+0x294/0x754
        ...

The memory leak problem was introduced as a side ef another fix in
regulator_register() error path, I believe that the proper fix is
to decouple device_register() function into its two compounds and
initialize a struct device before assigning any values to its fields
and then using it before actual registration of a device happens.

This lets to call put_device() safely after initialization, and, since
now a release callback is called, kfree(rdev->constraints) shall be
removed to exclude a double free condition.

Fixes: a3cde9534ebd ("regulator: core: fix regulator_register() error paths to properly release rdev")
Cc: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
---
 drivers/regulator/core.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 03154f5b939f..720f28844795 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -5023,7 +5023,6 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	struct regulator_dev *rdev;
 	bool dangling_cfg_gpiod = false;
 	bool dangling_of_gpiod = false;
-	bool reg_device_fail = false;
 	struct device *dev;
 	int ret, i;
 
@@ -5152,10 +5151,12 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	}
 
 	/* register with sysfs */
+	device_initialize(&rdev->dev);
 	rdev->dev.class = &regulator_class;
 	rdev->dev.parent = dev;
 	dev_set_name(&rdev->dev, "regulator.%lu",
 		    (unsigned long) atomic_inc_return(&regulator_no));
+	dev_set_drvdata(&rdev->dev, rdev);
 
 	/* set regulator constraints */
 	if (init_data)
@@ -5206,12 +5207,9 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	    !rdev->desc->fixed_uV)
 		rdev->is_switch = true;
 
-	dev_set_drvdata(&rdev->dev, rdev);
-	ret = device_register(&rdev->dev);
-	if (ret != 0) {
-		reg_device_fail = true;
+	ret = device_add(&rdev->dev);
+	if (ret != 0)
 		goto unset_supplies;
-	}
 
 	rdev_init_debugfs(rdev);
 
@@ -5233,17 +5231,15 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	mutex_unlock(&regulator_list_mutex);
 wash:
 	kfree(rdev->coupling_desc.coupled_rdevs);
-	kfree(rdev->constraints);
 	mutex_lock(&regulator_list_mutex);
 	regulator_ena_gpio_free(rdev);
 	mutex_unlock(&regulator_list_mutex);
+	put_device(&rdev->dev);
+	rdev = NULL;
 clean:
 	if (dangling_of_gpiod)
 		gpiod_put(config->ena_gpiod);
-	if (reg_device_fail)
-		put_device(&rdev->dev);
-	else
-		kfree(rdev);
+	kfree(rdev);
 	kfree(config);
 rinse:
 	if (dangling_cfg_gpiod)
-- 
2.24.0

Re: [PATCH] regulator: fix memory leak on error path of regulator_register()

[Mark Brown]

On Fri, 24 Jul 2020 03:50:13 +0300, Vladimir Zapolskiy wrote:
> The change corrects registration and deregistration on error path
> of a regulator, the problem was manifested by a reported memory
> leak on deferred probe:
> 
>     as3722-regulator as3722-regulator: regulator 13 register failed -517
> 
>     # cat /sys/kernel/debug/kmemleak
>     unreferenced object 0xecc43740 (size 64):
>       comm "swapper/0", pid 1, jiffies 4294937640 (age 712.880s)
>       hex dump (first 32 bytes):
>         72 65 67 75 6c 61 74 6f 72 2e 32 34 00 5a 5a 5a  regulator.24.ZZZ
>         5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
>       backtrace:
>         [<0c4c3d1c>] __kmalloc_track_caller+0x15c/0x2c0
>         [<40c0ad48>] kvasprintf+0x64/0xd4
>         [<109abd29>] kvasprintf_const+0x70/0x84
>         [<c4215946>] kobject_set_name_vargs+0x34/0xa8
>         [<62282ea2>] dev_set_name+0x40/0x64
>         [<a39b6757>] regulator_register+0x3a4/0x1344
>         [<16a9543f>] devm_regulator_register+0x4c/0x84
>         [<51a4c6a1>] as3722_regulator_probe+0x294/0x754
>         ...
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next

Thanks!

[1/1] regulator: fix memory leak on error path of regulator_register()
      commit: 9177514ce34902b3adb2abd490b6ad05d1cfcb43

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark