[PATCH] acpi: acpica: fix acpi operand cache leak
From: Seunghun Han
Date: Sat Feb 11 2017 - 21:51:11 EST
I'm Seunghun Han, and I work for National Security Research Institute of
South Korea.
I have been doing a research on ACPI and making a handcrafted ACPI table
for my research.
Errors of handcrafted ACPI tables are handled well in Linux kernel while boot
process, and Linux kernel goes well without critical problems.
But I found some ACPI operand cache leaks in ACPI early abort cases.
Boot log of ACPI operand cache leak is as follows:
>[ 0.174332] ACPI: Added _OSI(Module Device)
>[ 0.175504] ACPI: Added _OSI(Processor Device)
>[ 0.176010] ACPI: Added _OSI(3.0 _SCP Extensions)
>[ 0.177032] ACPI: Added _OSI(Processor Aggregator Device)
>[ 0.178284] ACPI: SCI (IRQ16705) allocation failed
>[ 0.179352] ACPI Exception: AE_NOT_ACQUIRED, Unable to install System Control Interrupt handler (20160930/evevent-131)
>[ 0.180008] ACPI: Unable to start the ACPI Interpreter
>[ 0.181125] ACPI Error: Could not remove SCI handler (20160930/evmisc-281)
>[ 0.184068] kmem_cache_destroy Acpi-Operand: Slab cache still has objects
>[ 0.185358] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.10.0-rc3 #2
>[ 0.186820] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
>[ 0.188000] Call Trace:
>[ 0.188000] ? dump_stack+0x5c/0x7d
>[ 0.188000] ? kmem_cache_destroy+0x224/0x230
>[ 0.188000] ? acpi_sleep_proc_init+0x22/0x22
>[ 0.188000] ? acpi_os_delete_cache+0xa/0xd
>[ 0.188000] ? acpi_ut_delete_caches+0x3f/0x7b
>[ 0.188000] ? acpi_terminate+0x5/0xf
>[ 0.188000] ? acpi_init+0x288/0x32e
>[ 0.188000] ? __class_create+0x4c/0x80
>[ 0.188000] ? video_setup+0x7a/0x7a
>[ 0.188000] ? do_one_initcall+0x4e/0x1b0
>[ 0.188000] ? kernel_init_freeable+0x194/0x21a
>[ 0.188000] ? rest_init+0x80/0x80
>[ 0.188000] ? kernel_init+0xa/0x100
>[ 0.188000] ? ret_from_fork+0x25/0x30
When early abort is occurred due to invalid ACPI information, Linux kernel
terminates ACPI by calling acpi_terminate() function.
The function calls acpi_ns_terminate() function to delete namespace data
and ACPI operand cache (acpi_gbl_module_code_list).
But the deletion code in acpi_ns_terminate() function is wrapped in
ACPI_EXEC_APP definition, therefore the code is only executed when the
definition exists.
If the define doesn't exist, ACPI operand cache (acpi_gbl_module_code_list) is
leaked, and stack dump is shown in kernel log.
This causes a security threat because the old kernel (<= 4.9) shows memory
locations of kernel functions in stack dump, therefore kernel ASLR can be
neutralized.
To fix ACPI operand leak for enhancing security, I made a patch which removes
the ACPI_EXEC_APP define in acpi_ns_terminate() function for executing the
deletion code unconditionally.
I hope that this patch improves the security of Linux kernel.
Thank you.
Signed-off-by: Seunghun Han <kkamagui@xxxxxxxxx>
---
drivers/acpi/acpica/nsutils.c | 26 +++++++++++---------------
1 file changed, 11 insertions(+), 15 deletions(-)
diff --git a/drivers/acpi/acpica/nsutils.c b/drivers/acpi/acpica/nsutils.c
index 691814d..acb6099 100644
--- a/drivers/acpi/acpica/nsutils.c
+++ b/drivers/acpi/acpica/nsutils.c
@@ -597,22 +597,18 @@ void acpi_ns_terminate(void)
ACPI_FUNCTION_TRACE(ns_terminate);
-#ifdef ACPI_EXEC_APP
- {
- union acpi_operand_object *prev;
- union acpi_operand_object *next;
-
- /* Delete any module-level code blocks */
-
- next = acpi_gbl_module_code_list;
- while (next) {
- prev = next;
- next = next->method.mutex;
- prev->method.mutex = NULL; /* Clear the Mutex (cheated) field */
- acpi_ut_remove_reference(prev);
- }
+ union acpi_operand_object *prev;
+ union acpi_operand_object *next;
+
+ /* Delete any module-level code blocks */
+
+ next = acpi_gbl_module_code_list;
+ while (next) {
+ prev = next;
+ next = next->method.mutex;
+ prev->method.mutex = NULL; /* Clear the Mutex (cheated) field */
+ acpi_ut_remove_reference(prev);
}
-#endif
/*
* Free the entire namespace -- all nodes and all objects
--
2.1.4