linux-kernel - Re: [PATCH v5] powerpc: Do not make the entire heap executable

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Message-ID: <20160929160702.GA30031@redhat.com>
Date:   Thu, 29 Sep 2016 18:07:02 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Al Viro <viro@...iv.linux.org.uk>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Florian Weimer <fweimer@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] powerpc: Do not make the entire heap executable

On 09/28, Kees Cook wrote:
>
> This is where the flags are actually built from what's coming in
> through the newly created exported function vm_brk_flags() below. The
> only flag we're acting on is VM_EXEC (passed in from set_brk() above).
> I think do_brk_flags() should mask the valid flags, or we'll regret it
> in the future. I'd like to see something like:
>
>     /* Until we need other flags, refuse anything except VM_EXEC. */
>     if ((flags & (~VM_EXEC)) != 0)
>         return -EINVAL;
>     flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;

I tried to suggest this too. In particular it would be simply wrong
to accept VM_LOCKED in flags.

Oleg.