linux-kernel - Re: [PATCH 6/7] pipe: simplify round_pipe

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]

Date:   Tue, 9 Jan 2018 18:52:01 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Willy Tarreau <w@....eu>,
        Mikulas Patocka <mpatocka@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 6/7] pipe: simplify round_pipe_size()

On Tue, Jan 09, 2018 at 02:27:10PM -0800, Kees Cook wrote:
> 
> > @@ -1054,9 +1048,6 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
> >                 return -EINVAL;
> >         nr_pages = size >> PAGE_SHIFT;
> >
> > -       if (!nr_pages)
> > -               return -EINVAL;
> > -
> 
> I would just leave this hunk anyway: it's defensive for any future
> changes. Maybe add a comment describing why it's currently redundant?
> 

I don't know; I find it really confusing to have two slightly different checks
for the same thing, as it implies that they actually need to be there for a
reason.  How about just checking nr_pages?

        size = round_pipe_size(arg);
        nr_pages = size >> PAGE_SHIFT;

        if (nr_pages == 0)
                return -EINVAL;

Eric