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Date: Tue, 4 Jul 2017 17:51:40 +0200
From: Willy Tarreau <w@1wt.eu>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: Michal Hocko <mhocko@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Oleg Nesterov <oleg@redhat.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>, Rik van Riel <riel@redhat.com>,
        Larry Woodman <lwoodman@redhat.com>,
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        Tony Luck <tony.luck@intel.com>,
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        Qualys Security Advisory <qsa@qualys.com>,
        LKML <linux-kernel@vger.kernel.org>, Ximin Luo <infinity0@debian.org>
Subject: Re: [PATCH] mm: larger stack guard gap, between vmas
Message-ID: <20170704155140.GC22013@1wt.eu>
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On Tue, Jul 04, 2017 at 12:36:11PM +0100, Ben Hutchings wrote:
> > If anywhing this would require to have a loop over all PROT_NONE
> > mappings to not hit into other weird usecases.
> 
> That's what I was thinking of.  Tried the following patch:
(...)
> -	next = vma->vm_next;
> +	/*
> +	 * Allow VM_NONE mappings in the gap as some applications try
> +	 * to make their own stack guards
> +	 */
> +	for (next = vma->vm_next;
> +	     next && !(next->vm_flags & (VM_READ | VM_WRITE | VM_EXEC));
> +	     next = next->vm_next)
> +		;

That's what I wanted to propose but I feared someone would scream at me
for this loop :-)

+1 for me!

Willy