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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200726163422.GA24657@lst.de>
Date:   Sun, 26 Jul 2020 18:34:22 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>, 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 05:32:14PM +0100, Al Viro wrote:
> > +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...

The main reason it is there is to preserve the previous semantics.
And no, I don't think we actually need it on x86.  But what if some
poor souls adds a BE version that needs this?  E.g. arm oabi has similar
weird alignment, and now imagine someone adding arm64 compat code for
that..