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[209.85.217.52]) by smtp.gmail.com with ESMTPSA id 187sm691383vku.45.2019.04.17.22.31.18 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 22:31:19 -0700 (PDT) Received: by mail-vs1-f52.google.com with SMTP id w13so512588vsc.4 for ; Wed, 17 Apr 2019 22:31:18 -0700 (PDT) X-Received: by 2002:a67:bc13:: with SMTP id t19mr2611825vsn.222.1555565478030; Wed, 17 Apr 2019 22:31:18 -0700 (PDT) MIME-Version: 1.0 References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-10-alex@ghiti.fr> In-Reply-To: <20190417052247.17809-10-alex@ghiti.fr> From: Kees Cook Date: Thu, 18 Apr 2019 00:31:06 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 09/11] mips: 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-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Apr 17, 2019 at 12:32 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 Acked-by: Kees Cook -Kees > --- > arch/mips/mm/mmap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c > index 3ff82c6f7e24..ffbe69f3a7d9 100644 > --- a/arch/mips/mm/mmap.c > +++ b/arch/mips/mm/mmap.c > @@ -22,7 +22,7 @@ EXPORT_SYMBOL(shm_align_mask); > > /* 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) > #define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > > static int mmap_is_legacy(struct rlimit *rlim_stack) > @@ -54,7 +54,7 @@ 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); > } > > #define COLOUR_ALIGN(addr, pgoff) \ > -- > 2.20.1 > -- Kees Cook