Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200603154559.140418-1-colin.king@canonical.com>
 <CAOQ4uxhLW=MSk=RhUi51EdOticfk1i_pku6qjCp2QpwnpyL5sw@mail.gmail.com>
 <1edc291d-6e63-89d8-d48c-443908ddc0e8@canonical.com> <CAJfpegsyGmJYHJr8rmRTxScYGyNQ1ZdPMxprW1zoQmGhXg1wuA@mail.gmail.com>
 <78e9b4ed-f530-1fd0-07a2-aca5245a6bd8@canonical.com>
In-Reply-To: <78e9b4ed-f530-1fd0-07a2-aca5245a6bd8@canonical.com>
From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 4 Jun 2020 11:39:24 +0200
Message-ID: <CAJfpegvnMrYdn0pqZLK7BaPmfwd_8Xf=vECd3GVDa6++bh9D7Q@mail.gmail.com>
Subject: Re: [PATCH][next] ovl: fix null pointer dereference on null stack
 pointer on error return
To:     Colin Ian King <colin.king@canonical.com>
Cc:     Amir Goldstein <amir73il@gmail.com>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        kernel-janitors@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jun 4, 2020 at 11:27 AM Colin Ian King <colin.king@canonical.com> wrote:
>
> On 04/06/2020 08:25, Miklos Szeredi wrote:
> > On Wed, Jun 3, 2020 at 6:15 PM Colin Ian King <colin.king@canonical.com> wrote:
> >>
> >> On 03/06/2020 17:11, Amir Goldstein wrote:
> >>> On Wed, Jun 3, 2020 at 6:46 PM Colin King <colin.king@canonical.com> wrote:
> >>>>
> >>>> From: Colin Ian King <colin.king@canonical.com>
> >>>>
> >>>> There are two error return paths where the call to path_put is
> >>>> dereferencing the null pointer 'stack'.  Fix this by avoiding the
> >>>> error exit path via label 'out_err' that will lead to the path_put
> >>>> calls and instead just return the error code directly.
> >>>>
> >>>> Addresses-Coverity: ("Dereference after null check)"
> >>>> Fixes: 4155c10a0309 ("ovl: clean up getting lower layers")
> >>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >>>
> >>>
> >>> Which branch is that based on?
> >>> Doesn't seem to apply to master nor next
> >>
> >> It was based on today's linux-next
> >
> > Yeah, it's actually
> >
> > Fixes: 73819e26c0f0 ("ovl: get rid of redundant members in struct ovl_fs")
> >
> > So I'll just fold your patch.  There's still a change in the loop
> > count for later errors, but that's okay, since
> > ovl_lower_dir()/ovl_mount_dir_noesc() use the path_put_init() variant.
> > Actually ovl_lower_dir() can get rid of that path_put_init()
> > completely, since now the only caller will take care of that...
> >
> > Thanks for reporting!
> >
> > Miklos
> >
> Is there a reason for folding the fix and hence losing the Signed-off-by
> tag?

I generally prefer to fold small fixes for not yet merged patches.  In
this case it's more of a personal preference, but in other cases it
might have an effect on bisectability.

Thanks,
Miklos