linux-kernel - Re: [PATCH 1/2] fs: btrfs: Fix error path kobject memory leak

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Message-ID: <20190513071131.GD2868@kroah.com>
Date:   Mon, 13 May 2019 09:11:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Nikolay Borisov <nborisov@...e.com>
Cc:     "Tobin C. Harding" <tobin@...nel.org>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] fs: btrfs: Fix error path kobject memory leak

On Mon, May 13, 2019 at 08:59:56AM +0300, Nikolay Borisov wrote:
> 
> 
> On 13.05.19 г. 6:39 ч., Tobin C. Harding wrote:
> > If a call to kobject_init_and_add() fails we must call kobject_put()
> > otherwise we leak memory.
> > 
> > Calling kobject_put() when kobject_init_and_add() fails drops the
> > refcount back to 0 and calls the ktype release method.
> > 
> > Add call to kobject_put() in the error path of call to
> > kobject_init_and_add().
> > 
> > Signed-off-by: Tobin C. Harding <tobin@...nel.org>
> > ---
> >  fs/btrfs/extent-tree.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> > index c5880329ae37..5e40c8f1e97a 100644
> > --- a/fs/btrfs/extent-tree.c
> > +++ b/fs/btrfs/extent-tree.c
> > @@ -3981,8 +3981,7 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags)
> >  				    info->space_info_kobj, "%s",
> >  				    alloc_name(space_info->flags));
> >  	if (ret) {
> > -		percpu_counter_destroy(&space_info->total_bytes_pinned);
> > -		kfree(space_info);
> > +		kobject_put(&space_info->kobj);
> 
> If you are only fixing kobject-related code then why do you delete
> correct code as well? percpu_counter_Destroy is needed to dispose of the
> percpu state which might have been allocated in percpu_counter_init
> based on whether CONFIG_SMP is enabled or not? Also, the call to kfree
> is required.

Both of those will happen in space_info_release() when the kobject is
properly disposed of with this last put to the kobject reference.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>