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Date: Thu, 29 Sep 2016 18:07:02 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Kees Cook <keescook@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>, Al Viro <viro@zeniv.linux.org.uk>,
 "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
 Andrew Morton <akpm@linux-foundation.org>,
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 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
 Florian Weimer <fweimer@redhat.com>, Linux-MM <linux-mm@kvack.org>,
 LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5] powerpc: Do not make the entire heap executable
Message-ID: <20160929160702.GA30031@redhat.com>
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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.