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([2a00:1fa0:8c7:ada9:25b2:24d8:3973:eb87]) by smtp.gmail.com with ESMTPSA id f23sm406561lfc.25.2019.08.08.02.16.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Aug 2019 02:16:17 -0700 (PDT) Subject: Re: [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap To: Alexandre Ghiti , Andrew Morton Cc: Paul Walmsley , Luis Chamberlain , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Kees Cook , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20190808061756.19712-1-alex@ghiti.fr> <20190808061756.19712-10-alex@ghiti.fr> From: Sergei Shtylyov Message-ID: Date: Thu, 8 Aug 2019 12:16:04 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190808061756.19712-10-alex@ghiti.fr> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hello! On 08.08.2019 9:17, Alexandre Ghiti wrote: > This commit takes care of stack randomization and stack guard gap when > computing mmap base address and checks if the task asked for randomization. > > This fixes the problem uncovered and not fixed for arm here: > https://lkml.kernel.org/r/20170622200033.25714-1-riel@redhat.com > > Signed-off-by: Alexandre Ghiti > Acked-by: Kees Cook > Acked-by: Paul Burton > Reviewed-by: Luis Chamberlain > --- > arch/mips/mm/mmap.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c > index d79f2b432318..f5c778113384 100644 > --- a/arch/mips/mm/mmap.c > +++ b/arch/mips/mm/mmap.c > @@ -21,8 +21,9 @@ unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */ > EXPORT_SYMBOL(shm_align_mask); > > /* gap between mmap and stack */ > -#define MIN_GAP (128*1024*1024UL) > -#define MAX_GAP ((TASK_SIZE)/6*5) > +#define MIN_GAP (128*1024*1024UL) > +#define MAX_GAP ((TASK_SIZE)/6*5) Could add spaces around *, while touching this anyway? And parens around TASK_SIZE shouldn't be needed... > +#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > > static int mmap_is_legacy(struct rlimit *rlim_stack) > { > @@ -38,6 +39,15 @@ static int mmap_is_legacy(struct rlimit *rlim_stack) > static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > { > unsigned long gap = rlim_stack->rlim_cur; > + unsigned long pad = stack_guard_gap; > + > + /* Account for stack randomization if necessary */ > + if (current->flags & PF_RANDOMIZE) > + pad += (STACK_RND_MASK << PAGE_SHIFT); Parens not needed here. > + > + /* Values close to RLIM_INFINITY can overflow. */ > + if (gap + pad > gap) > + gap += pad; > > if (gap < MIN_GAP) > gap = MIN_GAP; >