From mboxrd@z Thu Jan 1 00:00:00 1970 From: stewart@linux.vnet.ibm.com (Stewart Smith) Date: Wed, 13 Jul 2016 14:59:51 +1000 Subject: [RFC 0/3] extend kexec_file_load system call In-Reply-To: <20160712221804.GV1041@n2100.armlinux.org.uk> References: <20160712014201.11456-1-takahiro.akashi@linaro.org> <87furf7ztv.fsf@x220.int.ebiederm.org> <50662781.Utjsnse3nb@hactar> <20160712225805.0d27fe5d@hananiah.suse.cz> <20160712221804.GV1041@n2100.armlinux.org.uk> Message-ID: <87twfunneg.fsf@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Russell King - ARM Linux writes: > On Tue, Jul 12, 2016 at 10:58:05PM +0200, Petr Tesarik wrote: >> I'm not an expert on DTB, so I can't provide an example of code >> execution, but you have already mentioned the /chosen/linux,stdout-path >> property. If an attacker redirects the bootloader to an insecure >> console, they may get access to the system that would otherwise be >> impossible. > > I fail to see how kexec connects with the boot loader - the DTB image > that's being talked about is one which is passed from the currently > running kernel to the to-be-kexec'd kernel. For ARM (and I suspect > also ARM64) that's a direct call chain which doesn't involve any > boot loader or firmware, and certainly none that would involve the > passed DTB image. For OpenPOWER machines, kexec is the bootloader. Our bootloader is a linux kernel and initramfs with a UI (petitboot) - this means we never have to write a device driver twice: write a kernel one and you're done (for booting from the device and using it in your OS). -- Stewart Smith OPAL Architect, IBM.