netdev - Re: [PATCH 04/11] iov_iter: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check

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Message-ID: <20200921150745.GT3421308@ZenIV.linux.org.uk>
Date:   Mon, 21 Sep 2020 16:07:45 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        David Laight <David.Laight@...lab.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-aio@...ck.org, io-uring@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        netdev@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH 04/11] iov_iter: explicitly check for CHECK_IOVEC_ONLY in
 rw_copy_check_uvector

On Mon, Sep 21, 2020 at 04:34:27PM +0200, Christoph Hellwig wrote:
> Explicitly check for the magic value insted of implicitly relying on
> its numeric representation.   Also drop the rather pointless unlikely
> annotation.

See above - I would rather have CHECK_IOVEC_ONLY gone.

The reason for doing these access_ok() in the same loop is fairly weak,
especially since you are checking type on each iteration.  Might as
well do that in a separate loop afterwards.