linux-kernel - [PATCH] ACPI: APEI: EINJ: Fix resource leak by remove callback in .exit.text

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Message-ID: <20250814051157.35867-2-u.kleine-koenig@baylibre.com>
Date: Thu, 14 Aug 2025 07:11:57 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ira Weiny <ira.weiny@...el.com>,
	Zaid Alali <zaidal@...amperecomputing.com>,
	Colin Ian King <colin.i.king@...il.com>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>
Cc: Tony Luck <tony.luck@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	Hanjun Guo <guohanjun@...wei.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Shuai Xue <xueshuai@...ux.alibaba.com>,
	Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] ACPI: APEI: EINJ: Fix resource leak by remove callback in .exit.text

The .remove() callback is also used during error handling in
faux_probe(). As einj_remove() was marked with __exit it's not linked
into the kernel if the driver is built-in, potentially resulting in
resource leaks.

Also remove the comment justifying the __exit annotation which doesn't
apply any more since the driver was converted to the faux device
interface.

Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...libre.com>
---
Hello,

note that the intention seems to be that this construct is safe, see
commit c393befa14ab ("driver core: faux: Suppress bind attributes").
Note further that I don't have a machine to test that so this is only
based on code reading. An appropriate test might be:

| diff --git a/drivers/base/faux.c b/drivers/base/faux.c
| index f5fbda0a9a44..decb15f1194a 100644
| --- a/drivers/base/faux.c
| +++ b/drivers/base/faux.c
| @@ -39,6 +39,8 @@ static int faux_match(struct device *dev, const struct device_driver *drv)
|  	return 1;
|  }
|  
| +static int once;
| +
|  static int faux_probe(struct device *dev)
|  {
|  	struct faux_object *faux_obj = to_faux_object(dev);
| @@ -56,7 +58,11 @@ static int faux_probe(struct device *dev)
|  	 * Add groups after the probe succeeds to ensure resources are
|  	 * initialized correctly
|  	 */
| -	ret = device_add_groups(dev, faux_obj->groups);
| +
| +	if (once++)
| +		ret = -ENOMEM;
| +	else
| +		ret = device_add_groups(dev, faux_obj->groups);
|  	if (ret && faux_ops && faux_ops->remove)
|  		faux_ops->remove(faux_dev);
 
(quoted to make sure that this hunk won't be used when the patch is
applied).

Even if the faux device interface is fixed not to rely on .remove() the
comment in einj-core.c needs some love.

Best regards
Uwe

 drivers/acpi/apei/einj-core.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
index bf8dc92a373a..1204fa3df285 100644
--- a/drivers/acpi/apei/einj-core.c
+++ b/drivers/acpi/apei/einj-core.c
@@ -1091,7 +1091,7 @@ static int __init einj_probe(struct faux_device *fdev)
 	return rc;
 }
 
-static void __exit einj_remove(struct faux_device *fdev)
+static void einj_remove(struct faux_device *fdev)
 {
 	struct apei_exec_context ctx;
 
@@ -1114,15 +1114,9 @@ static void __exit einj_remove(struct faux_device *fdev)
 }
 
 static struct faux_device *einj_dev;
-/*
- * einj_remove() lives in .exit.text. For drivers registered via
- * platform_driver_probe() this is ok because they cannot get unbound at
- * runtime. So mark the driver struct with __refdata to prevent modpost
- * triggering a section mismatch warning.
- */
-static struct faux_device_ops einj_device_ops __refdata = {
+static struct faux_device_ops einj_device_ops = {
 	.probe = einj_probe,
-	.remove = __exit_p(einj_remove),
+	.remove = einj_remove,
 };
 
 static int __init einj_init(void)

base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
-- 
2.50.1