From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valerie Aurora Subject: Re: [PATCH 5/7 v3] vfs: fix possible use after free in finish_open() Date: Thu, 23 Sep 2010 16:19:19 -0400 Message-ID: <20100923201919.GC3536@shell> References: <20100920180404.939991832@szeredi.hu> <20100920180446.104998543@szeredi.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, neilb@suse.de, viro@zeniv.linux.org.uk, stable@kernel.org To: Miklos Szeredi Return-path: Content-Disposition: inline In-Reply-To: <20100920180446.104998543@szeredi.hu> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Sep 20, 2010 at 08:04:09PM +0200, Miklos Szeredi wrote: > From: Miklos Szeredi > > If open(O_TRUNC) is called and the actual open fails, then nd->path > will be released by nameidata_to_filp(). If this races with an > unmount then mnt_drop_write() can Oops. > > Fix by acquiring a ref to nd->path and releasing after > mnt_drop_write(). > > Signed-off-by: Miklos Szeredi > CC: stable@kernel.org > --- > fs/namei.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > Index: linux-2.6/fs/namei.c > =================================================================== > --- linux-2.6.orig/fs/namei.c 2010-09-20 13:32:35.000000000 +0200 > +++ linux-2.6/fs/namei.c 2010-09-20 13:33:14.000000000 +0200 > @@ -1559,6 +1559,11 @@ static struct file *finish_open(struct n > mnt_drop_write(nd->path.mnt); > goto exit; > } > + if (will_truncate) { > + /* nameidata_to_filp() puts nd->path! */ > + path_get(&nd->path); > + } > + > filp = nameidata_to_filp(nd); > if (!IS_ERR(filp)) { > error = ima_file_check(filp, acc_mode); > @@ -1581,8 +1586,10 @@ static struct file *finish_open(struct n > * because the filp has had a write taken > * on its behalf. > */ > - if (will_truncate) > + if (will_truncate) { > mnt_drop_write(nd->path.mnt); > + path_put(&nd->path); > + } > return filp; > > exit: > Nice catch! Reviewed-by: Valerie Aurora -VAL