From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: Re: [PATCH v3 2/2] efi: efi_mem_reserve(): don't reserve through memblock after mm_init() Date: Mon, 9 Jan 2017 13:00:33 +0000 Message-ID: <20170109130033.GH16838@codeblueprint.co.uk> References: <20170105125130.2815-1-nicstange@gmail.com> <20170105125130.2815-2-nicstange@gmail.com> <87wpe8mjdk.fsf@gmail.com> <87showm682.fsf@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ard Biesheuvel Cc: Nicolai Stange , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , Mika =?iso-8859-1?Q?Penttil=E4?= , Dan Williams , Dave Young , "linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-efi@vger.kernel.org On Fri, 06 Jan, at 07:28:40PM, Ard Biesheuvel wrote: > > This is my point exactly. But it appears efi_free_boot_services() > occurs much later than I thought, and so there is a sizabe time window > where SLAB is up but reservations can still be made. But we don't > check whether efi_free_boot_services() has been called. True. This has only been correct thus far because all code has been audited, but adding a check to catch future offenders is a good idea. > Another problem is that we never check that the reservation is > covered by a BootServicesData region, which are the only ones that > are guaranteed to be retained up to this point. The runtime regions are guaranteed to be retained too. Again, this shouldn't actually be a problem today, but the potential for breakage here warrants some kind of check and loud warning.