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[217.70.183.197]) by mx.google.com with ESMTPS id w23si655982eji.29.2019.04.17.23.01.26 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Apr 2019 23:01:26 -0700 (PDT) Received-SPF: neutral (google.com: 217.70.183.197 is neither permitted nor denied by best guess record for domain of alex@ghiti.fr) client-ip=217.70.183.197; Authentication-Results: mx.google.com; spf=neutral (google.com: 217.70.183.197 is neither permitted nor denied by best guess record for domain of alex@ghiti.fr) smtp.mailfrom=alex@ghiti.fr X-Originating-IP: 79.86.19.127 Received: from [192.168.0.11] (127.19.86.79.rev.sfr.net [79.86.19.127]) (Authenticated sender: alex@ghiti.fr) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id D2FD11C0008; Thu, 18 Apr 2019 06:01:20 +0000 (UTC) Subject: Re: [PATCH v3 05/11] arm: Properly account for stack randomization and stack guard gap To: Kees Cook Cc: Albert Ou , Catalin Marinas , Palmer Dabbelt , Will Deacon , Russell King , Ralf Baechle , LKML , Linux-MM , Paul Burton , linux-riscv@lists.infradead.org, Alexander Viro , James Hogan , "linux-fsdevel@vger.kernel.org" , Andrew Morton , linux-mips@vger.kernel.org, Christoph Hellwig , linux-arm-kernel , Luis Chamberlain References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-6-alex@ghiti.fr> From: Alex Ghiti Message-ID: Date: Thu, 18 Apr 2019 02:01:20 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: sv-FI X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/18/19 1:26 AM, Kees Cook wrote: > On Wed, Apr 17, 2019 at 12:28 AM 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://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html > Please use the official archive instead. This includes headers, linked > patches, etc: > https://lkml.kernel.org/r/20170622200033.25714-1-riel@redhat.com Ok, sorry about that, and thanks for the info. > >> Signed-off-by: Alexandre Ghiti >> --- >> arch/arm/mm/mmap.c | 14 ++++++++++++-- >> 1 file changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c >> index f866870db749..bff3d00bda5b 100644 >> --- a/arch/arm/mm/mmap.c >> +++ b/arch/arm/mm/mmap.c >> @@ -18,8 +18,9 @@ >> (((pgoff)<> >> /* gap between mmap and stack */ >> -#define MIN_GAP (128*1024*1024UL) >> -#define MAX_GAP ((TASK_SIZE)/6*5) >> +#define MIN_GAP (128*1024*1024UL) > Might as well fix this up as SIZE_128M I left the code as is because it gets removed in the next commit, I did not even correct the checkpatch warnings. But I can fix that in v4, since there will be a v4 :) > >> +#define MAX_GAP ((TASK_SIZE)/6*5) >> +#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > STACK_RND_MASK is already defined so you don't need to add it here, yes? At this point, I don't think arm has STACK_RND_MASK defined anywhere since the generic version is in mm/util.c. > >> static int mmap_is_legacy(struct rlimit *rlim_stack) >> { >> @@ -35,6 +36,15 @@ 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); >> + >> + /* Values close to RLIM_INFINITY can overflow. */ >> + if (gap + pad > gap) >> + gap += pad; >> >> if (gap < MIN_GAP) >> gap = MIN_GAP; >> -- >> 2.20.1 >> > But otherwise, yes: > > Acked-by: Kees Cook Thanks ! > > -- > Kees Cook > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv