linux-kernel - Re: [PATCH v3] kset: fix memory leak when kset

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Message-ID: <Y1gVj6Uq2NDScYdY@kroah.com>
Date:   Tue, 25 Oct 2022 18:57:51 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yang Yingliang <yangyingliang@...wei.com>
Cc:     linux-kernel@...r.kernel.org, qemu-devel@...gnu.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-erofs@...ts.ozlabs.org, ocfs2-devel@....oracle.com,
        linux-mtd@...ts.infradead.org, amd-gfx@...ts.freedesktop.org,
        rafael@...nel.org, somlo@....edu, mst@...hat.com,
        jaegeuk@...nel.org, chao@...nel.org, hsiangkao@...ux.alibaba.com,
        huangjianan@...o.com, mark@...heh.com, jlbec@...lplan.org,
        joseph.qi@...ux.alibaba.com, akpm@...ux-foundation.org,
        alexander.deucher@....com, luben.tuikov@....com, richard@....at,
        liushixin2@...wei.com
Subject: Re: [PATCH v3] kset: fix memory leak when kset_register() returns
 error

On Tue, Oct 25, 2022 at 03:15:49PM +0800, Yang Yingliang wrote:
> Inject fault while loading module, kset_register() may fail.
> If it fails, the kset.kobj.name allocated by kobject_set_name()
> which must be called before a call to kset_register() may be
> leaked, since refcount of kobj was set in kset_init().
> 
> To mitigate this, we free the name in kset_register() when an
> error is encountered, i.e. when kset_register() returns an error.
> 
> A kset may be embedded in a larger structure which may be dynamically
> allocated in callers, it needs to be freed in ktype.release() or error
> path in callers, in this case, we can not call kset_put() in kset_register(),
> or it will cause double free, so just call kfree_const() to free the
> name and set it to NULL to avoid accessing bad pointer in callers.
> 
> With this fix, the callers don't need care about freeing the name
> and may call kset_put() if kset_register() fails.
> 
> Suggested-by: Luben Tuikov <luben.tuikov@....com>
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> ---
> v2 -> v3:
>   Update commit message and comment of kset_register().
> 
> v1 -> v2:
>   Free name inside of kset_register() instead of calling kset_put()
>   in drivers.

Thank you for all of this, it's a much nicer and cleaner fix than
forcing all callers to try to handle it instead.

greg k-h