Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 15 Mar 2021 17:19:29 +0100 | Subject | Re: [PATCH 1/1] ACPI: fix acpi table use after free |
| |
On Sun, Mar 14, 2021 at 8:00 PM Mike Rapoport <rppt@linux.ibm.com> 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 <david@redhat.com> 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.
However, it looks to me that something like the following could be done to start with:
(a) Make __acpi_map_table() call memblock_reserve() in addition to early_memremap().
My assumption here is that the memblock_reserve() will simply be ignored if it is called too late.
(b) Introduce acpi_reserve_tables() as something like
void __init acpi_table_reserve(void) { acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0); }
Because initial_tables is passed to acpi_initialize_tables() above and allow_resize is 0, the array used by it will simply get overwritten when acpi_table_init() gets called.
(c) Make setup_arch() call acpi_table_reserve() like in the original patch from George.
Would that work?
If so, I'll cut a patch along these lines.
| |