linux-kernel - Re: [PATCH v2] iov_iter: don't revert iov buffer if csum error

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Message-ID: <20170429024647.GO29622@ZenIV.linux.org.uk>
Date:   Sat, 29 Apr 2017 03:46:47 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Ding Tianhong <dingtianhong@...wei.com>
Cc:     David Miller <davem@...emloft.net>, pabeni@...hat.com,
        edumazet@...gle.com, hannes@...essinduktion.org,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        LinuxArm <linuxarm@...wei.com>,
        "weiyongjun (A)" <weiyongjun1@...wei.com>
Subject: Re: [PATCH v2] iov_iter: don't revert iov buffer if csum error

On Sat, Apr 29, 2017 at 10:38:48AM +0800, Ding Tianhong wrote:
> The patch 327868212381 (make skb_copy_datagram_msg() et.al. preserve
> ->msg_iter on error) will revert the iov buffer if copy to iter
> failed, but it didn't copy any datagram if the skb_checksum_complete
> error, so no need to revert any data at this place.

The bug is real, but I would suggest a simpler fix:
                if (__skb_checksum_complete(skb))
                        return -EINVAL;
leaving the rest as-is.