linux-kernel - Re: CVE-2016-7097 causes acl leak

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Message-ID: <3a180415-2f02-c9c0-e1e6-519b5d3115b7@android.com>
Date:   Mon, 12 Dec 2016 16:26:00 -0800
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        aneesh.kumar@...ux.vnet.ibm.com, Jan Kara <jack@...e.cz>
Subject: Re: CVE-2016-7097 causes acl leak

On 12/11/2016 04:34 PM, Cong Wang wrote:
> On Mon, Dec 5, 2016 at 9:16 AM, Mark Salyzyn <salyzyn@...roid.com> wrote:
>> Commit 073931017b49d9458aa351605b43a7e34598caef has several occurrences of
>> an acl leak.
>>
>> posix_acl_update_mode(inose, &mode, &acl);
>>
>> . . .
>>
>> posix_acl_release(acl);
>>
>>
>> acl is NULLed in posix_acl_update_mode to signal caller to not update the
>> acl; but because it is nulled, it is never released.
> I think you blame the wrong commit, this leak exists before that commit.
> Looks like we should just release it before NULL'ing.
>
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 5955220..edd862a 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -648,8 +648,10 @@ int posix_acl_update_mode(struct inode *inode,
> umode_t *mode_p,
>          error = posix_acl_equiv_mode(*acl, &mode);
>          if (error < 0)
>                  return error;
> -       if (error == 0)
> +       if (error == 0) {
> +               posix_acl_release(*acl);
>                  *acl = NULL;
> +       }
>          if (!in_group_p(inode->i_gid) &&
>              !capable_wrt_inode_uidgid(inode, CAP_FSETID))
>                  mode &= ~S_ISGID;

The leaks were introduced in 9p, gfs2, jfs and xfs drivers only.


-- Mark