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Date: Mon, 10 Jun 2024 11:11:39 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Rafael Aquini <aquini@redhat.com>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>, Heiko
 Carstens <hca@linux.ibm.com>, Petr Mladek <pmladek@suse.com>, Mike Rapoport
 <rppt@kernel.org>, Paul McKenney <paulmck@kernel.org>, Samuel Holland
 <samuel.holland@sifive.com>
Subject: Re: [PATCH v2] mm: mmap: allow for the maximum number of bits for
 randomizing mmap_base by default
Message-Id: <20240610111139.1e392360ffe847ea48ffebab@linux-foundation.org>
In-Reply-To: <20240606180622.102099-1-aquini@redhat.com>
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On Thu,  6 Jun 2024 14:06:22 -0400 Rafael Aquini <aquini@redhat.com> wrote:

> An ASLR regression was noticed [1] and tracked down to file-mapped areas
> being backed by THP in recent kernels. The 21-bit alignment constraint
> for such mappings reduces the entropy for randomizing the placement of
> 64-bit library mappings and breaks ASLR completely for 32-bit libraries.
> 
> The reported issue is easily addressed by increasing vm.mmap_rnd_bits
> and vm.mmap_rnd_compat_bits. This patch just provides a simple way to
> set ARCH_MMAP_RND_BITS and ARCH_MMAP_RND_COMPAT_BITS to their maximum
> values allowed by the architecture at build time.
> 
> [1] https://zolutal.github.io/aslrnt/

Are we able to identify a Fixes: target for this?

I assume a cc:stable is appropriate?