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Date:   Thu, 13 Dec 2018 12:10:01 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc:     linux-fsdevel@vger.kernel.org, amir73il@gmail.com,
        zohar@linux.ibm.com,
        syzbot+ae82084b07d0297e566b@syzkaller.appspotmail.com,
        syzkaller-bugs@googlegroups.com, linux-integrity@vger.kernel.org,
        linux-unionfs@vger.kernel.org, dvyukov@google.com
Subject: Re: [PATCH] fs: Evaluate O_WRONLY | O_RDWR to O_RDWR
Message-ID: <20181213121000.GM2217@ZenIV.linux.org.uk>
References: <20181213115717.p7ncktng2ihxw5md@merlin>
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On Thu, Dec 13, 2018 at 05:57:17AM -0600, Goldwyn Rodrigues wrote:
> A user can open(O_WRONLY | O_RDWR) and the options are valid.
> However, OPEN_FMODE() evaluates both FMODE_READ and FMODE_WRITE,
> as negative. We also need to protect the lower layers from this
> anomaly.
> 
> Solve it by dropping O_WRONLY, so O_RDWR takes precedence.

Congratulations, you've broken fdutils...  Passing 3 in lower bits
of open() flags is *not* the same as O_RDWR; behaiviour is
different and deliberately chosen by existing userland code.

IOW, NAK.