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Fri, 25 Sep 2020 13:37:12 -0700 (PDT) X-Gm-Message-State: AOAM532yJQ9eyLqfIg/4tqHUXMot1b/lLw/NnySreM4zyJBdRaiSGVzH CLKxlKCikemk1Sb5fX7aKQhuwVoDm2vMCKNqg+I= X-Google-Smtp-Source: ABdhPJy5yn+k2qTffdPEkwz81q4jfUywaUdKX4eyqIezGZqX1pvY0kQk58CIUkInD4MoUX3cSwW3s41Wr8o4wcTAQO8= X-Received: by 2002:a4a:4910:: with SMTP id z16mr2063269ooa.41.1601066231895; Fri, 25 Sep 2020 13:37:11 -0700 (PDT) MIME-Version: 1.0 References: <202009251301.A1FD183582@keescook> In-Reply-To: <202009251301.A1FD183582@keescook> From: Ard Biesheuvel Date: Fri, 25 Sep 2020 22:37:01 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: KASLR support on ARM with Kernel 4.9 and 4.14 To: Kees Cook X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200925_163714_980579_5AC69F17 X-CRM114-Status: GOOD ( 29.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Thomas Garnier , Pintu Agarwal , Arnd Bergmann , Ard Biesheuvel , Marc Zyngier , Kernelnewbies , Russell King - ARM Linux , open list , Tony Lindgren , nico@linaro.org, Dave Martin , matt@codeblueprint.co.uk, "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 25 Sep 2020 at 22:28, Kees Cook wrote: > > On Fri, Sep 25, 2020 at 08:33:59PM +0530, Pintu Agarwal wrote: > > This is regarding the KASLR feature support on ARM for the kernel > > version 4.9 and 4.14. > > > > Is KASLR supported on ARM-32 Linux 4.9 and above ? > > Sorry, this feature did not yet land in upstream: > https://github.com/KSPP/linux/issues/3 > > Here was the earlier effort: > https://lore.kernel.org/kernel-hardening/20170814125411.22604-1-ard.biesheuvel@linaro.org/ > > > Is it dependent on CONFIG_RANDOMIZE_BASE or > > CONFIG_RANDOMIZE_BASE is what is used on other architectures to control > the feature. > > > /proc/sys/kernel/randomize_va_space ? > > Is there any relation between these two? > > No, the latter is about userspace addresses. > > > Is the changing kernel symbols (in every boot), only possible if KASLR > > is enabled, or there is another way it can happen? > > I think you meant kernel symbol addresses (not the symbols themselves). > But yes, I wouldn't expect the addresses to move if you didn't either > rebuild the kernel or had something else moving the kernel at boot (i.e. > the boot loader). > > > I have these queries because, > > In one of the arm-32 devices with Kernel 4.14, I observed that > > CONFIG_RANDOMIZE_BASE is not available. > > But /proc/sys/kernel/randomize_va_space is set to 2. > > However, I also observed that symbol addresses are changing in every boot. > > > > 1st boot cycle: > > [root ~]# cat /proc/kallsyms | grep "sys_open" > > a5b4de92 T sys_open > > [root@sa515m ~]# > > > > 2nd boot cycle: > > [root ~]# cat /proc/kallsyms | grep "sys_open" > > f546ed66 T sys_open > > > > So, I am wondering how this is possible without KASLR > > (CONFIG_RANDOMIZE_BASE) support in Kernel ? > Those addresses were obfuscated by kptr_restrict _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel