linux-kernel - RE: [PATCH 3/3] quota: simplify the quotactl compat handling

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Message-ID: <f894de9f065f4bf9a451668dfbf35591@AcuMS.aculab.com>
Date:   Fri, 7 Aug 2020 09:38:38 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@....de>,
        "x86@...nel.org" <x86@...nel.org>, "Jan Kara" <jack@...e.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Jan Kara <jack@...e.cz>
Subject: RE: [PATCH 3/3] quota: simplify the quotactl compat handling

From: Christoph Hellwig
> Sent: 31 July 2020 13:22
> 
> Fold the misaligned u64 workarounds into the main quotactl flow instead
> of implementing a separate compat syscall handler.
> 
...
> +static int compat_copy_fs_quota_stat(struct compat_fs_quota_stat __user *to,
> +		struct fs_quota_stat *from)
> +{
> +	if (put_user(from->qs_version, &to->qs_version) ||
> +	    put_user(from->qs_flags, &to->qs_flags) ||
> +	    put_user(from->qs_pad, &to->qs_pad) ||
> +	    compat_copy_fs_qfilestat(&to->qs_uquota, &from->qs_uquota) ||
> +	    compat_copy_fs_qfilestat(&to->qs_gquota, &from->qs_gquota) ||
> +	    put_user(from->qs_incoredqs, &to->qs_incoredqs) ||
> +	    put_user(from->qs_btimelimit, &to->qs_btimelimit) ||
> +	    put_user(from->qs_itimelimit, &to->qs_itimelimit) ||
> +	    put_user(from->qs_rtbtimelimit, &to->qs_rtbtimelimit) ||
> +	    put_user(from->qs_bwarnlimit, &to->qs_bwarnlimit) ||
> +	    put_user(from->qs_iwarnlimit, &to->qs_iwarnlimit))
> +		return -EFAULT;
> +	return 0;
> +}

That might look better as a 'noinline' function that copied
all the fields into an on-stack struct compat_fs_quota_stat
and then did a single copy_to_user().

(I do 'like' qs_pad - I wonder what the person who added
it was smoking.)

	David

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