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

[George Kennedy]

Since commit 7fef431be9c9 ("mm/page_alloc: place pages to tail
in __free_pages_core()") the following use after free occurs
intermittently when acpi tables are accessed.

BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
Read of size 4 at addr ffff8880be453004 by task swapper/0/1
CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.12.0-rc1-7a7fd0d #1
Call Trace:
 dump_stack+0xf6/0x158
 print_address_description.constprop.9+0x41/0x60
 kasan_report.cold.14+0x7b/0xd4
 __asan_report_load_n_noabort+0xf/0x20
 ibft_init+0x134/0xc49
 do_one_initcall+0xc4/0x3e0
 kernel_init_freeable+0x5af/0x66b
 kernel_init+0x16/0x1d0
 ret_from_fork+0x22/0x30

ACPI tables mapped via kmap() do not have their mapped pages
reserved and the pages can be "stolen" by the buddy allocator.
Use memblock_reserve() to reserve all the ACPI table pages.

Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx>
---
 arch/x86/kernel/setup.c        | 3 +--
 drivers/acpi/acpica/tbinstal.c | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d883176..97deea3 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1046,6 +1046,7 @@ void __init setup_arch(char **cmdline_p)
 	cleanup_highmap();
 
 	memblock_set_current_limit(ISA_END_ADDRESS);
+	acpi_boot_table_init();
 	e820__memblock_setup();
 
 	/*
@@ -1139,8 +1140,6 @@ void __init setup_arch(char **cmdline_p)
 	/*
 	 * Parse the ACPI tables for possible boot-time SMP configuration.
 	 */
-	acpi_boot_table_init();
-
 	early_acpi_boot_init();
 
 	initmem_init();
diff --git a/drivers/acpi/acpica/tbinstal.c b/drivers/acpi/acpica/tbinstal.c
index 8d1e5b5..4e32b22 100644
--- a/drivers/acpi/acpica/tbinstal.c
+++ b/drivers/acpi/acpica/tbinstal.c
@@ -8,6 +8,7 @@
  *****************************************************************************/
 
 #include <acpi/acpi.h>
+#include <linux/memblock.h>
 #include "accommon.h"
 #include "actables.h"
 
@@ -58,6 +59,9 @@
 				      new_table_desc->flags,
 				      new_table_desc->pointer);
 
+	memblock_reserve(new_table_desc->address,
+			 PAGE_ALIGN(new_table_desc->pointer->length));
+
 	acpi_tb_print_table_header(new_table_desc->address,
 				   new_table_desc->pointer);
 
-- 
1.8.3.1