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[209.85.221.177]) by smtp.gmail.com with ESMTPSA id h143sm326652vkh.12.2019.04.17.22.28.05 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 22:28:05 -0700 (PDT) Received: by mail-vk1-f177.google.com with SMTP id h71so214190vkf.5 for ; Wed, 17 Apr 2019 22:28:05 -0700 (PDT) X-Received: by 2002:a1f:2e07:: with SMTP id u7mr49260276vku.44.1555565284857; Wed, 17 Apr 2019 22:28:04 -0700 (PDT) MIME-Version: 1.0 References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-7-alex@ghiti.fr> In-Reply-To: <20190417052247.17809-7-alex@ghiti.fr> From: Kees Cook Date: Thu, 18 Apr 2019 00:27:53 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 06/11] arm: Use STACK_TOP when computing mmap base address 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-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Wed, Apr 17, 2019 at 12:29 AM Alexandre Ghiti wrote: > > mmap base address must be computed wrt stack top address, using TASK_SIZE > is wrong since STACK_TOP and TASK_SIZE are not equivalent. > > Signed-off-by: Alexandre Ghiti > --- > arch/arm/mm/mmap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c > index bff3d00bda5b..0b94b674aa91 100644 > --- a/arch/arm/mm/mmap.c > +++ b/arch/arm/mm/mmap.c > @@ -19,7 +19,7 @@ > > /* gap between mmap and stack */ > #define MIN_GAP (128*1024*1024UL) > -#define MAX_GAP ((TASK_SIZE)/6*5) > +#define MAX_GAP ((STACK_TOP)/6*5) Parens around STACK_TOP aren't needed, but you'll be removing it entirely, so I can't complain. ;) > #define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > > static int mmap_is_legacy(struct rlimit *rlim_stack) > @@ -51,7 +51,7 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > else if (gap > MAX_GAP) > gap = MAX_GAP; > > - return PAGE_ALIGN(TASK_SIZE - gap - rnd); > + return PAGE_ALIGN(STACK_TOP - gap - rnd); > } > > /* > -- > 2.20.1 > Acked-by: Kees Cook -- Kees Cook