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[209.85.217.50]) by smtp.gmail.com with ESMTPSA id d6sm223199uad.10.2019.04.17.21.37.12 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 21:37:12 -0700 (PDT) Received: by mail-vs1-f50.google.com with SMTP id g187so451935vsc.8 for ; Wed, 17 Apr 2019 21:37:12 -0700 (PDT) X-Received: by 2002:a67:7c8a:: with SMTP id x132mr50675686vsc.172.1555562232106; Wed, 17 Apr 2019 21:37:12 -0700 (PDT) MIME-Version: 1.0 References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-4-alex@ghiti.fr> In-Reply-To: <20190417052247.17809-4-alex@ghiti.fr> From: Kees Cook Date: Wed, 17 Apr 2019 23:37:00 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 03/11] arm64: Consider stack randomization for mmap base only when necessary To: Alexandre Ghiti Cc: Andrew Morton , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Luis Chamberlain , Kees Cook , LKML , linux-arm-kernel , linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, "linux-fsdevel@vger.kernel.org" , Linux-MM Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Apr 17, 2019 at 12:26 AM Alexandre Ghiti wrote: > > Do not offset mmap base address because of stack randomization if > current task does not want randomization. Maybe mention that this makes this logic match the existing x86 behavior too? > Signed-off-by: Alexandre Ghiti Acked-by: Kees Cook -Kees > --- > arch/arm64/mm/mmap.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c > index ed4f9915f2b8..ac89686c4af8 100644 > --- a/arch/arm64/mm/mmap.c > +++ b/arch/arm64/mm/mmap.c > @@ -65,7 +65,11 @@ unsigned long arch_mmap_rnd(void) > static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > { > unsigned long gap = rlim_stack->rlim_cur; > - unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap; > + unsigned long pad = stack_guard_gap; > + > + /* Account for stack randomization if necessary */ > + if (current->flags & PF_RANDOMIZE) > + pad += (STACK_RND_MASK << PAGE_SHIFT); > > /* Values close to RLIM_INFINITY can overflow. */ > if (gap + pad > gap) > -- > 2.20.1 > -- Kees Cook