From: Miklos Szeredi <miklos@szeredi.hu>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>,
"linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ovl: fix uid/gid when creating over whiteout
Date: Wed, 15 Jun 2016 16:09:47 +0200 [thread overview]
Message-ID: <CAJfpegvopC3wA9YQ9J5khG3nCJ9zeXTpZ-SMj515vF5RMXEhNQ@mail.gmail.com> (raw)
In-Reply-To: <20160615140151.GB19388@redhat.com>
On Wed, Jun 15, 2016 at 4:01 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> On Wed, Jun 15, 2016 at 03:30:02PM +0200, Miklos Szeredi wrote:
>> --- a/fs/overlayfs/dir.c
>> +++ b/fs/overlayfs/dir.c
>> @@ -405,12 +405,21 @@ static int ovl_create_or_link(struct den
>> err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
>> } else {
>> const struct cred *old_cred;
>> + struct cred *override_cred;
>>
>> old_cred = ovl_override_creds(dentry->d_sb);
>>
>> - err = ovl_create_over_whiteout(dentry, inode, &stat, link,
>> - hardlink);
>> + err = -ENOMEM;
>> + override_cred = prepare_creds();
>> + if (override_cred) {
>> + override_cred->fsuid = old_cred->fsuid;
>> + override_cred->fsgid = old_cred->fsgid;
>
> Hi Miklos,
>
> I am wondering if we are switching to tasks's ->fsuid and ->fsgid too
> early. ovl_create_over_whiteout() calls ovl_lookup_temp(workdir) and
> IIUC, task might not have permission to do lookup in workdir.
>
> Should we switch to this override_cred, just before ovl_create_real()
> so that task ->fsuid and ->fsgid are used only for creation purposes
> only.
For lookup in workdir only CAP_DAC_OVERRIDE should matter, the actual
value of the fsuid and fsgid should be irrelevant (user, group and
others all have zero permission on workdir).
Thanks,
Miklos
next prev parent reply other threads:[~2016-06-15 14:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-15 13:30 [PATCH] ovl: fix uid/gid when creating over whiteout Miklos Szeredi
2016-06-15 14:01 ` Vivek Goyal
2016-06-15 14:09 ` Miklos Szeredi [this message]
2016-06-15 14:20 ` Vivek Goyal
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