Messages in this thread Patch in this message | | | Subject | Re: [PATCH 00/11] fix memory leak while kset_register() fails | From | Yang Yingliang <> | Date | Fri, 21 Oct 2022 16:59:46 +0800 |
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On 2022/10/21 16:36, Greg KH wrote: > On Fri, Oct 21, 2022 at 04:24:23PM +0800, Yang Yingliang wrote: >> On 2022/10/21 13:37, Greg KH wrote: >>> On Fri, Oct 21, 2022 at 01:29:31AM -0400, Luben Tuikov wrote: >>>> 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. >>> Based on this, can kset_register() just clean up from itself when an >>> error happens? Ideally that would be the case, as the odds of a kset >>> being embedded in a larger structure is probably slim, but we would have >>> to search the tree to make sure. >> I have search the whole tree, the kset used in bus_register() - patch #3, >> kset_create_and_add() - patch #4 >> __class_register() - patch #5, fw_cfg_build_symlink() - patch #6 and >> amdgpu_discovery.c - patch #10 >> is embedded in a larger structure. In these cases, we can not call >> kset_put() in error path in kset_register() > Yes you can as the kobject in the kset should NOT be controling the > lifespan of those larger objects. > > If it is, please point out the call chain here as I don't think that > should be possible. > > Note all of this is a mess because the kobject name stuff was added much > later, after the driver model had been created and running for a while. > We missed this error path when adding the dynamic kobject name logic, > thank for looking into this. > > If you could test the patch posted with your error injection systems, > that could make this all much simpler to solve.
The patch posted by Luben will cause double free in some cases.
From 71e0a22801c0699f67ea40ed96e0a7d7d9e0f318 Mon Sep 17 00:00:00 2001 From: Luben Tuikov <luben.tuikov@amd.com> Date: Fri, 21 Oct 2022 03:34:21 -0400 Subject: [PATCH] kobject: Add kset_put() if kset_register() fails X-check-string-leak: v1.0
If kset_register() fails, we call kset_put() before returning the error. This makes sure that we free memory allocated by kobj_set_name() for the kset, since kset_register() cannot be called unless the kset has a name, usually gotten via kobj_set_name(&kset->kobj, format, ...);
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Rafael J. Wysocki <rafael@kernel.org> Cc: Yang Yingliang <yangyingliang@huawei.com> Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Signed-off-by: Luben Tuikov <luben.tuikov@amd.com> --- lib/kobject.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/lib/kobject.c b/lib/kobject.c index a0b2dbfcfa2334..c122b979f2b75e 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -844,8 +844,10 @@ int kset_register(struct kset *k)
kset_init(k); err = kobject_add_internal(&k->kobj); - if (err) + if (err) { + kset_put(k); return err; + } kobject_uevent(&k->kobj, KOBJ_ADD); return 0; } -- 2.38.0-rc2 > > thanks, > > greg k-h > .
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