linux-kernel - Re: [PATCH 4/4] quota: simplify the quotactl compat handling

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Message-ID: <20200726163214.GS2786714@ZenIV.linux.org.uk>
Date:   Sun, 26 Jul 2020 17:32:14 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     x86@...nel.org, Jan Kara <jack@...e.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling

On Sun, Jul 26, 2020 at 06:04:01PM +0200, Christoph Hellwig wrote:
> Fold the misaligned u64 workarounds into the main quotactl flow instead
> of implementing a separate compat syscall handler.

I can live with that (and drop the local quota-related stuff from
copy_in_user/compat_alloc_user_space elimination series).  One question,
though:

> +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
> +		struct fs_qfilestat *from)
> +{
> +	if (copy_to_user(to, from, sizeof(*to)) ||
> +	    put_user(from->qfs_nextents, &to->qfs_nextents))
> +		return -EFAULT;
> +	return 0;
> +}

do we have any need of that put_user()?  Note that you don't even call
that thing unless compat_need_64bit_alignment_fixup() is true.  And AFAICS
all such cases are little-endian...