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* [PATCH] [v4] module: don't ignore sysfs_create_link() failures
@ 2024-04-08  8:05 Arnd Bergmann
  2024-04-08 16:00 ` Luis Chamberlain
  0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2024-04-08  8:05 UTC (permalink / raw
  To: Luis Chamberlain
  Cc: Arnd Bergmann, Greg Kroah-Hartman, linux-modules,
	Rafael J. Wysocki, Jens Axboe, linux-kernel

From: Arnd Bergmann <arnd@arndb.de>

The sysfs_create_link() return code is marked as __must_check, but the
module_add_driver() function tries hard to not care, by assigning the
return code to a variable. When building with 'make W=1', gcc still
warns because this variable is only assigned but not used:

drivers/base/module.c: In function 'module_add_driver':
drivers/base/module.c:36:6: warning: variable 'no_warn' set but not used [-Wunused-but-set-variable]

Rework the code to properly unwind and return the error code to the
caller. My reading of the original code was that it tries to
not fail when the links already exist, so keep ignoring -EEXIST
errors.

Fixes: e17e0f51aeea ("Driver core: show drivers in /sys/module/")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
See-also: 4a7fb6363f2d ("add __must_check to device management code")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
Luis, can you merge this through the modules-next tree?

Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: linux-modules@vger.kernel.org
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
---
v4: minor style changes, based on feedback from Andy Shevchenko
v3: make error handling stricter, add unwinding,
     fix build fail with CONFIG_MODULES=n
v2: rework to actually handle the error. I have not tested the
    error handling beyond build testing, so please review carefully.
---
 drivers/base/base.h   |  9 ++++++---
 drivers/base/bus.c    |  9 ++++++++-
 drivers/base/module.c | 42 +++++++++++++++++++++++++++++++-----------
 3 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 0738ccad08b2..db4f910e8e36 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -192,11 +192,14 @@ extern struct kset *devices_kset;
 void devices_kset_move_last(struct device *dev);
 
 #if defined(CONFIG_MODULES) && defined(CONFIG_SYSFS)
-void module_add_driver(struct module *mod, struct device_driver *drv);
+int module_add_driver(struct module *mod, struct device_driver *drv);
 void module_remove_driver(struct device_driver *drv);
 #else
-static inline void module_add_driver(struct module *mod,
-				     struct device_driver *drv) { }
+static inline int module_add_driver(struct module *mod,
+				    struct device_driver *drv)
+{
+	return 0;
+}
 static inline void module_remove_driver(struct device_driver *drv) { }
 #endif
 
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index daee55c9b2d9..ffea0728b8b2 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -674,7 +674,12 @@ int bus_add_driver(struct device_driver *drv)
 		if (error)
 			goto out_del_list;
 	}
-	module_add_driver(drv->owner, drv);
+	error = module_add_driver(drv->owner, drv);
+	if (error) {
+		printk(KERN_ERR "%s: failed to create module links for %s\n",
+			__func__, drv->name);
+		goto out_detach;
+	}
 
 	error = driver_create_file(drv, &driver_attr_uevent);
 	if (error) {
@@ -699,6 +704,8 @@ int bus_add_driver(struct device_driver *drv)
 
 	return 0;
 
+out_detach:
+	driver_detach(drv);
 out_del_list:
 	klist_del(&priv->knode_bus);
 out_unregister:
diff --git a/drivers/base/module.c b/drivers/base/module.c
index 46ad4d636731..a1b55da07127 100644
--- a/drivers/base/module.c
+++ b/drivers/base/module.c
@@ -30,14 +30,14 @@ static void module_create_drivers_dir(struct module_kobject *mk)
 	mutex_unlock(&drivers_dir_mutex);
 }
 
-void module_add_driver(struct module *mod, struct device_driver *drv)
+int module_add_driver(struct module *mod, struct device_driver *drv)
 {
 	char *driver_name;
-	int no_warn;
 	struct module_kobject *mk = NULL;
+	int ret;
 
 	if (!drv)
-		return;
+		return 0;
 
 	if (mod)
 		mk = &mod->mkobj;
@@ -56,17 +56,37 @@ void module_add_driver(struct module *mod, struct device_driver *drv)
 	}
 
 	if (!mk)
-		return;
+		return 0;
+
+	ret = sysfs_create_link(&drv->p->kobj, &mk->kobj, "module");
+	if (ret)
+		return ret;
 
-	/* Don't check return codes; these calls are idempotent */
-	no_warn = sysfs_create_link(&drv->p->kobj, &mk->kobj, "module");
 	driver_name = make_driver_name(drv);
-	if (driver_name) {
-		module_create_drivers_dir(mk);
-		no_warn = sysfs_create_link(mk->drivers_dir, &drv->p->kobj,
-					    driver_name);
-		kfree(driver_name);
+	if (!driver_name) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	module_create_drivers_dir(mk);
+	if (!mk->drivers_dir) {
+		ret = -EINVAL;
+		goto out;
 	}
+
+	ret = sysfs_create_link(mk->drivers_dir, &drv->p->kobj, driver_name);
+	if (ret)
+		goto out;
+
+	kfree(driver_name);
+
+	return 0;
+out:
+	sysfs_remove_link(&drv->p->kobj, "module");
+	sysfs_remove_link(mk->drivers_dir, driver_name);
+	kfree(driver_name);
+
+	return ret;
 }
 
 void module_remove_driver(struct device_driver *drv)
-- 
2.39.2


^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-04-11 12:42 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2024-04-08  8:05 [PATCH] [v4] module: don't ignore sysfs_create_link() failures Arnd Bergmann
2024-04-08 16:00 ` Luis Chamberlain
2024-04-11 12:42   ` Greg Kroah-Hartman

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