Re: [PATCH 1/1] ACPI: fix acpi table use after free

Rafael J. Wysocki
2021-03-17T20:15:29Z

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 <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.

So maybe something like the patch below?

I'm not sure if acpi_boot_table_prepare() gets called early enough, though.

Also this still may not play well with initrd-based table overrides. Erik, do
you have any insights here?

And ia64 needs to be updated too.

---
arch/x86/kernel/acpi/boot.c | 12 +++++++++---
arch/x86/kernel/setup.c | 3 +++
drivers/acpi/tables.c | 24 +++++++++++++++++++++---
include/linux/acpi.h | 9 +++++++--
4 files changed, 40 insertions(+), 8 deletions(-)

Index: linux-pm/arch/x86/kernel/acpi/boot.c
===================================================================
--- linux-pm.orig/arch/x86/kernel/acpi/boot.c
+++ linux-pm/arch/x86/kernel/acpi/boot.c
@@ -1541,7 +1541,7 @@ static const struct dmi_system_id acpi_d
* ...
*/

-void __init acpi_boot_table_init(void)
+void __init acpi_boot_table_prepare(void)
{
dmi_check_system(acpi_dmi_table);

@@ -1554,10 +1554,16 @@ void __init acpi_boot_table_init(void)
/*
* Initialize the ACPI boot-time table parser.
*/
- if (acpi_table_init()) {
+ if (acpi_table_prepare())
disable_acpi();
+}
+
+void __init acpi_boot_table_init(void)
+{
+ if (acpi_disabled)
return;
- }
+
+ acpi_table_init();

acpi_table_parse(ACPI_SIG_BOOT, acpi_parse_sbf);

Index: linux-pm/arch/x86/kernel/setup.c
===================================================================
--- linux-pm.orig/arch/x86/kernel/setup.c
+++ linux-pm/arch/x86/kernel/setup.c
@@ -1070,6 +1070,9 @@ void __init setup_arch(char **cmdline_p)
/* preallocate 4k for mptable mpc */
e820__memblock_alloc_reserved_mpc_new();

+ /* Look for ACPI tables and reserve memory occupied by them. */
+ acpi_boot_table_prepare();
+
#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
setup_bios_corruption_check();
#endif
Index: linux-pm/include/linux/acpi.h
===================================================================
--- linux-pm.orig/include/linux/acpi.h
+++ linux-pm/include/linux/acpi.h
@@ -222,11 +222,13 @@ void __iomem *__acpi_map_table(unsigned
void __acpi_unmap_table(void __iomem *map, unsigned long size);
int early_acpi_boot_init(void);
int acpi_boot_init (void);
+void acpi_boot_table_prepare (void);
void acpi_boot_table_init (void);
int acpi_mps_check (void);
int acpi_numa_init (void);

-int acpi_table_init (void);
+int acpi_table_prepare (void);
+void acpi_table_init (void);
int acpi_table_parse(char *id, acpi_tbl_table_handler handler);
int __init acpi_table_parse_entries(char *id, unsigned long table_size,
int entry_id,
@@ -814,9 +816,12 @@ static inline int acpi_boot_init(void)
return 0;
}

+static inline void acpi_boot_table_prepare(void)
+{
+}
+
static inline void acpi_boot_table_init(void)
{
- return;
}

static inline int acpi_mps_check(void)
Index: linux-pm/drivers/acpi/tables.c
===================================================================
--- linux-pm.orig/drivers/acpi/tables.c
+++ linux-pm/drivers/acpi/tables.c
@@ -788,9 +788,10 @@ acpi_status acpi_os_table_override(struc
* result: sdt_entry[] is initialized
*/

-int __init acpi_table_init(void)
+int __init acpi_table_prepare(void)
{
acpi_status status;
+ int i;

if (acpi_verify_table_checksum) {
pr_info("Early table checksum verification enabled\n");
@@ -803,12 +804,29 @@ int __init acpi_table_init(void)
status = acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0);
if (ACPI_FAILURE(status))
return -EINVAL;
- acpi_table_initrd_scan();

- check_multiple_madt();
+ for (i = 0; i < ACPI_MAX_TABLES; i++) {
+ struct acpi_table_desc *table_desc = &initial_tables[i];
+
+ if (!table_desc->address || !table_desc->length)
+ break;
+
+ pr_info("Reserving %4s table memory at [0x%llx - 0x%llx]\n",
+ table_desc->signature.ascii, table_desc->address,
+ table_desc->address + table_desc->length - 1);
+
+ memblock_reserve(table_desc->address, table_desc->length);
+ }
+
return 0;
}

+void __init acpi_table_init(void)
+{
+ acpi_table_initrd_scan();
+ check_multiple_madt();
+}
+
static int __init acpi_parse_apic_instance(char *str)
{
if (!str)