(Note at bottom on reasons for 'To' list 'Cc' list)
Hi,
kobject_init_and_add() seems to be routinely misused. A failed call to this
function requires a call to kobject_put() otherwise we leak memory.
Examples memleaks can be seen in:
mm/slub.c
fs/btrfs/sysfs.c
fs/xfs/xfs_sysfs.h: xfs_sysfs_init()
Question: Do we fix the misuse or fix the API?
$ git grep kobject_init_and_add | wc -l
117
Either way, we will have to go through all 117 call sites and check them. I
don't mind fixing them all but I don't want to do it twice because I chose the
wrong option. Reaching out to those more experienced for a suggestion please.
Fix the API
-----------
Typically init functions do not require cleanup if they fail, this argument
leads to this patch
diff --git a/lib/kobject.c b/lib/kobject.c
index aa89edcd2b63..62328054bbd0 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -453,6 +453,9 @@ int kobject_init_and_add(struct kobject *kobj, struct
kobj_type *ktype,
retval = kobject_add_varg(kobj, parent, fmt, args);
va_end(args);
+ if (retval)
+ kobject_put(kobj);
+
return retval;
}
EXPORT_SYMBOL_GPL(kobject_init_and_add);
Fix all the call sites
----------------------
Go through all 117 call sites and add kobj_put() in the error path.
This example from mm/slub.c
diff --git a/mm/slub.c b/mm/slub.c
index d30ede89f4a6..84a9d6c06c27 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5756,8 +5756,10 @@ static int sysfs_slab_add(struct kmem_cache *s)
s->kobj.kset = kset;
err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
- if (err)
+ if (err) {
+ kobject_put(&s->kobj);
goto out;
+ }
err = sysfs_create_group(&s->kobj, &slab_attr_group);
if (err)
thanks,
Tobin.
This is a Saturday afternoon 'drinking some wine, hacking on the kernel'
email. Sending it to the lib/kobject.c maintainers for obvious
reasons. CC'd a few extra people who I thought might be interested to
take the weight of Greg and Rafael :)
