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Mon, 08 Jul 2019 07:46:34 -0700 (PDT) Date: Mon, 8 Jul 2019 07:46:32 -0700 From: Tejun Heo To: Hillf Danton Cc: syzbot , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: WARNING in kernfs_create_dir_ns Message-ID: <20190708144632.GB657710@devbig004.ftw2.facebook.com> References: <0000000000003ec128058c7624ec@google.com> <0000000000003bbf1b058c83f55a@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000003bbf1b058c83f55a@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Jul 01, 2019 at 01:52:35PM +0800, Hillf Danton wrote: > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_get fs/kernfs/dir.c:493 [inline] > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_new_node fs/kernfs/dir.c:700 [inline] > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022 ... > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -53,6 +53,10 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns) > if (!parent) > return -ENOENT; > > + /* create dir if parent is not dying */ > + if (!atomic_inc_not_zero(&parent->count)) > + return -ENOENT; > + > kobject_get_ownership(kobj, &uid, &gid); > > kn = kernfs_create_dir_ns(parent, kobject_name(kobj), > @@ -61,10 +65,12 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns) > if (IS_ERR(kn)) { > if (PTR_ERR(kn) == -EEXIST) > sysfs_warn_dup(parent, kobject_name(kobj)); > + kernfs_put(parent); > return PTR_ERR(kn); > } > > kobj->sd = kn; > + kernfs_put(parent); I don't think this is the correct fix. It's being called with kobj whose parent's sysfs node is dangling. It gotta be fixed from the caller side. Thanks. -- tejun