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From: Patrick Pannuto on 22 Jul 2010 18:10 There is a subtle memory leak in driver core error path. Consider the simplified view of bus_register (drivers/base/bus.c): priv = kzalloc... kobject_set_name(&priv->subsys.kobj,...) <== allocate in priv->subsys.kobj.name if kset_register(&priv->subsys) FAILS: (1) -- need to free name string here! goto out else keep going, assume we fail later... err_path_after_kset_register: kset_unregister(&priv->subsys) <== calls kobject_put(&priv->subsys->kobj), which is the last reference, which leads to kobject_cleanup, which frees the name field BUT DOES NOT SET IT TO NULL out: (2) Other place we could free name kfree(bus->p) // bus->p = priv ... Thus, we cannot insert the free'ing of name on the error path (2) since it will be indeterminite if we need to free the name string or not. kset_register cannot (and should not) free the name string if it fails since the caller may have other ideas, leaving only (1) as a viable location to free the name string. A walk-through of the failure path that will trigger this leak: bus_register(struct bus_type *bus) { ... priv = kzalloc... kobject_set_name(&priv->subsys.kobj,... { kobject_set_name_vargs(kobj,... { kobj->name = kvasprintf... <== ALLOCATE INTO &priv->subsys.kobj.name priv->subsys.kobj.kset = bus_kset priv->subsys.kobj.ktype = &bus_ktype retval = kset_register(&priv->subsys)... if (retval) YES goto out; ... out: kfree(bus->p); bus->p = NULL; return retval; } kset_register(struct kset *k) { // k = &priv->subsys kset_init(k) { kobject_init_internal(&k->kobj) { kref_init(&kobj->kref) { kref->refcount = 1 err = kobject_add_internal(&k->kobj)... if (err) YES return err; ... } kobject_add_internal(struct kobject *kobj) { // kobj = &priv->subsys.kobj ... if (kobj->kset) YES { kobj_kset_join(kobj) { kset_get(kobj->kset) <== bus_kset ... error = create_dir(kobj); if (error) YES { kobj_kset_leave(kobj) { kset_put(kobj->kset) <== bus_kset ... (release parent and make KERN_ERR noise) } return error } Signed-off-by: Patrick Pannuto <ppannuto(a)codeaurora.org> --- drivers/base/bus.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/drivers/base/bus.c b/drivers/base/bus.c index eb1b7fa..fea1774 100644 --- a/drivers/base/bus.c +++ b/drivers/base/bus.c @@ -900,8 +900,10 @@ int bus_register(struct bus_type *bus) priv->drivers_autoprobe = 1; retval = kset_register(&priv->subsys); - if (retval) + if (retval) { + kfree(priv->subsys.kobj.name); goto out; + } retval = bus_create_file(bus, &bus_attr_uevent); if (retval) -- 1.7.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |