Re: [PATCH 00/11] fix memory leak while kset_register() fails

Luben Tuikov
2022-10-21T05:30:11Z

On 2022-10-20 22:20, Yang Yingliang wrote:
> The previous discussion link:
> https://lore.kernel.org/lkml/0db486eb-6927-927e-3629-958f8f211194@huawei.com/T/

The very first discussion on this was here:

https://www.spinics.net/lists/dri-devel/msg368077.html

Please use this link, and not the that one up there you which quoted above,
and whose commit description is taken verbatim from the this link.

>
> kset_register() is currently used in some places without calling
> kset_put() in error path, because the callers think it should be
> kset internal thing to do, but the driver core can not know what
> caller doing with that memory at times. The memory could be freed
> both in kset_put() and error path of caller, if it is called in
> kset_register().

As I explained in the link above, the reason there's
a memory leak is that one cannot call kset_register() without
the kset->kobj.name being set--kobj_add_internal() returns -EINVAL,
in this case, i.e. kset_register() fails with -EINVAL.

Thus, the most common usage is something like this:

kobj_set_name(&kset->kobj, format, ...);
kset->kobj.kset = parent_kset;
kset->kobj.ktype = ktype;
res = kset_register(kset);

So, what is being leaked, is the memory allocated in kobj_set_name(),
by the common idiom shown above. This needs to be mentioned in
the documentation, at least, in case, in the future this is absolved
in kset_register() redesign, etc.

Regards,
Luben

>
> So make the function documentation more explicit about calling
> kset_put() in the error path of caller first, so that people
> have a chance to know what to do here, then fixes this leaks
> by calling kset_put() from callers.
>
> Liu Shixin (1):
> ubifs: Fix memory leak in ubifs_sysfs_init()
>
> Yang Yingliang (10):
> kset: fix documentation for kset_register()
> kset: add null pointer check in kset_put()
> bus: fix possible memory leak in bus_register()
> kobject: fix possible memory leak in kset_create_and_add()
> class: fix possible memory leak in __class_register()
> firmware: qemu_fw_cfg: fix possible memory leak in
> fw_cfg_build_symlink()
> f2fs: fix possible memory leak in f2fs_init_sysfs()
> erofs: fix possible memory leak in erofs_init_sysfs()
> ocfs2: possible memory leak in mlog_sys_init()
> drm/amdgpu/discovery: fix possible memory leak
>
> drivers/base/bus.c | 4 +++-
> drivers/base/class.c | 6 ++++++
> drivers/firmware/qemu_fw_cfg.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 5 +++--
> fs/erofs/sysfs.c | 4 +++-
> fs/f2fs/sysfs.c | 4 +++-
> fs/ocfs2/cluster/masklog.c | 7 ++++++-
> fs/ubifs/sysfs.c | 2 ++
> include/linux/kobject.h | 3 ++-
> lib/kobject.c | 5 ++++-
> 10 files changed, 33 insertions(+), 9 deletions(-)