linux-kernel - Re: [PATCH 05/14] fs: don't allow kernel reads and writes without iter ops

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:   Fri, 9 Oct 2020 18:03:31 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 05/14] fs: don't allow kernel reads and writes without
 iter ops

On Fri, Oct 9, 2020 at 3:06 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> It's a bit unintuitive that ppos=NULL means "use pos 0", not "use file->f_pos".

That's not at all what it means.

A NULL ppos means "this has no position at all", and is what we use
for FMODE_STREAM file descriptors (ie sockets, pipes, etc).

It also means that we don't do the locking for position updates.

The fact that "ki_pos" gets set to zero is just because it needs to be
_something_. It shouldn't actually ever be used for stream devices.

                  Linus