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Wysocki" Date: Thu, 18 Mar 2021 16:22:37 +0100 Message-ID: Subject: Re: [PATCH 1/1] ACPI: fix acpi table use after free To: Mike Rapoport Cc: "Rafael J. Wysocki" , Erik Kaneda , David Hildenbrand , George Kennedy , Robert Moore , Rafael Wysocki , Len Brown , ACPI Devel Maling List , "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" , Linux Kernel Mailing List , Konrad Rzeszutek Wilk , Dan Carpenter , Dhaval Giani , Andrew Morton , Vlastimil Babka , Oscar Salvador , Wei Yang , Pankaj Gupta , Michal Hocko Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 18, 2021 at 11:50 AM Rafael J. Wysocki wrote: > > On Thu, Mar 18, 2021 at 8:25 AM Mike Rapoport wrote: > > > > On Wed, Mar 17, 2021 at 09:14:37PM +0100, Rafael J. Wysocki wrote: > > > On Monday, March 15, 2021 5:19:29 PM CET Rafael J. Wysocki wrote: > > > > On Sun, Mar 14, 2021 at 8:00 PM Mike Rapoport wrote: > > > > > > > > > > On Thu, Mar 11, 2021 at 04:36:31PM +0100, Rafael J. Wysocki wrote: > > > > > > On Wed, Mar 10, 2021 at 8:47 PM David Hildenbrand wrote: > > > > > > > > > > > > > > > > There is some care that should be taken to make sure we get the order > > > > > > > > right, but I don't see a fundamental issue here. > > > > > > > > > > > > Me neither. > > > > > > > > > > > > > > If I understand correctly, Rafael's concern is about changing the parts of > > > > > > > > ACPICA that should be OS agnostic, so I think we just need another place to > > > > > > > > call memblock_reserve() rather than acpi_tb_install_table_with_override(). > > > > > > > > > > > > Something like this. > > > > > > > > > > > > There is also the problem that memblock_reserve() needs to be called > > > > > > for all of the tables early enough, which will require some reordering > > > > > > of the early init code. > > > > > > > > > > > > > > Since the reservation should be done early in x86::setup_arch() (and > > > > > > > > probably in arm64::setup_arch()) we might just have a function that parses > > > > > > > > table headers and reserves them, similarly to how we parse the tables > > > > > > > > during KASLR setup. > > > > > > > > > > > > Right. > > > > > > > > > > I've looked at it a bit more and we do something like the patch below that > > > > > nearly duplicates acpi_tb_parse_root_table() which is not very nice. > > > > > > > > It looks to me that the code need not be duplicated (see below). > > > > > > > > > Besides, reserving ACPI tables early and then calling acpi_table_init() > > > > > (and acpi_tb_parse_root_table() again would mean doing the dance with > > > > > early_memremap() twice for no good reason. > > > > > > > > That'd be simply inefficient which is kind of acceptable to me to start with. > > > > > > > > And I changing the ACPICA code can be avoided at least initially, it > > > > by itself would be a good enough reason. > > > > > > > > > I believe the most effective way to deal with this would be to have a > > > > > function that does parsing, reservation and installs the tables supplied by > > > > > the firmware which can be called really early and then another function > > > > > that overrides tables if needed a some later point. > > > > > > > > I agree that this should be the direction to go into. > > > > > > So maybe something like the patch below? > > > > > > I'm not sure if acpi_boot_table_prepare() gets called early enough, though. > > > > To be 100% safe it should be called before e820__memblock_setup(). > > OK Well, that said, reserve_bios_regions() doesn't seem to have concerns like this and I'm not sure why ACPI tables should be reserved before this runs. That applies to efi_reserve_boot_services() too. I can put the new call before e820__memblock_alloc_reserved_mpc_new(), but I'm not sure why to put it before efi_reserve_boot_services(), say?