From: Arnd Bergmann <[email protected]>
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.
Cc: Luis Chamberlain <[email protected]>
Cc: [email protected]
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Fixes: e17e0f51aeea ("Driver core: show drivers in /sys/module/")
See-also: 4a7fb6363f2d ("add __must_check to device management code")
Signed-off-by: Arnd Bergmann <[email protected]>
---
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..d16b5c8e5473 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;
+ int ret;
struct module_kobject *mk = NULL;
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
On Tue, Mar 26, 2024 at 03:57:18PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> 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.
> Cc: Luis Chamberlain <[email protected]>
> Cc: [email protected]
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
Wondering if you can move these to be after --- to avoid polluting commit
message. This will have the same effect and be archived on lore. But on
pros side it will unload the commit message(s) from unneeded noise.
..
> + error = module_add_driver(drv->owner, drv);
> + if (error) {
> + printk(KERN_ERR "%s: failed to create module links for %s\n",
> + __func__, drv->name);
What's wrong with pr_err()? Even if it's not a style used, in a new pieces of
code this can be improved beforehand. So, we will reduce a technical debt, and
not adding to it.
> + goto out_detach;
> + }
..
> +int module_add_driver(struct module *mod, struct device_driver *drv)
> {
> char *driver_name;
> - int no_warn;
> + int ret;
I would move it...
> struct module_kobject *mk = NULL;
..to be here.
--
With Best Regards,
Andy Shevchenko
On Tue, Mar 26, 2024 at 03:57:18PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> 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.
>
> Cc: Luis Chamberlain <[email protected]>
> Cc: [email protected]
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Fixes: e17e0f51aeea ("Driver core: show drivers in /sys/module/")
> See-also: 4a7fb6363f2d ("add __must_check to device management code")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> 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(-)
Reviewed-by: Greg Kroah-Hartman <[email protected]>
On Tue, Mar 26, 2024, at 16:29, Andy Shevchenko wrote:
> On Tue, Mar 26, 2024 at 03:57:18PM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <[email protected]>
>>
>> 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.
>
>> Cc: Luis Chamberlain <[email protected]>
>> Cc: [email protected]
>> Cc: Greg Kroah-Hartman <[email protected]>
>> Cc: "Rafael J. Wysocki" <[email protected]>
>
> Wondering if you can move these to be after --- to avoid polluting commit
> message. This will have the same effect and be archived on lore. But on
> pros side it will unload the commit message(s) from unneeded noise.
Done
>
>> + error = module_add_driver(drv->owner, drv);
>> + if (error) {
>> + printk(KERN_ERR "%s: failed to create module links for %s\n",
>> + __func__, drv->name);
>
> What's wrong with pr_err()? Even if it's not a style used, in a new pieces of
> code this can be improved beforehand. So, we will reduce a technical debt, and
> not adding to it.
I think that would be more confusing, and would rather keep the
style consistent. There is no practical difference here.
>> +int module_add_driver(struct module *mod, struct device_driver *drv)
>> {
>> char *driver_name;
>> - int no_warn;
>> + int ret;
>
> I would move it...
>
>> struct module_kobject *mk = NULL;
>
> ...to be here.
Done
Arnd