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ACPICA commit 8829e70e1360c81e7a5a901b5d4f48330e021ea5
I'm Seunghun Han, and I work for National Security Research Institute of
South Korea.
I have been doing a research on ACPI and found an ACPI cache leak in ACPI
early abort cases.
Boot log of ACPI cache leak is as follows:
[ 0.352414] ACPI: Added _OSI(Module Device)
[ 0.353182] ACPI: Added _OSI(Processor Device)
[ 0.353182] ACPI: Added _OSI(3.0 _SCP Extensions)
[ 0.353182] ACPI: Added _OSI(Processor Aggregator Device)
[ 0.356028] ACPI: Unable to start the ACPI Interpreter
[ 0.356799] ACPI Error: Could not remove SCI handler (20170303/evmisc-281)
[ 0.360215] kmem_cache_destroy Acpi-State: Slab cache still has objects
[ 0.360648] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W
4.12.0-rc4-next-20170608+ #10
[ 0.361273] Hardware name: innotek gmb_h virtual_box/virtual_box, BIOS
virtual_box 12/01/2006
[ 0.361873] Call Trace:
[ 0.362243] ? dump_stack+0x5c/0x81
[ 0.362591] ? kmem_cache_destroy+0x1aa/0x1c0
[ 0.362944] ? acpi_sleep_proc_init+0x27/0x27
[ 0.363296] ? acpi_os_delete_cache+0xa/0x10
[ 0.363646] ? acpi_ut_delete_caches+0x6d/0x7b
[ 0.364000] ? acpi_terminate+0xa/0x14
[ 0.364000] ? acpi_init+0x2af/0x34f
[ 0.364000] ? __class_create+0x4c/0x80
[ 0.364000] ? video_setup+0x7f/0x7f
[ 0.364000] ? acpi_sleep_proc_init+0x27/0x27
[ 0.364000] ? do_one_initcall+0x4e/0x1a0
[ 0.364000] ? kernel_init_freeable+0x189/0x20a
[ 0.364000] ? rest_init+0xc0/0xc0
[ 0.364000] ? kernel_init+0xa/0x100
[ 0.364000] ? ret_from_fork+0x25/0x30
I analyzed this memory leak in detail. I found that “Acpi-State” cache and
“Acpi-Parse” cache were merged because the size of cache objects was same
slab cache size.
I finally found “Acpi-Parse” cache and “Acpi-parse_ext” cache were leaked
using SLAB_NEVER_MERGE flag in kmem_cache_create() function.
Real ACPI cache leak point is as follows:
[ 0.360101] ACPI: Added _OSI(Module Device)
[ 0.360101] ACPI: Added _OSI(Processor Device)
[ 0.360101] ACPI: Added _OSI(3.0 _SCP Extensions)
[ 0.361043] ACPI: Added _OSI(Processor Aggregator Device)
[ 0.364016] ACPI: Unable to start the ACPI Interpreter
[ 0.365061] ACPI Error: Could not remove SCI handler (20170303/evmisc-281)
[ 0.368174] kmem_cache_destroy Acpi-Parse: Slab cache still has objects
[ 0.369332] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W
4.12.0-rc4-next-20170608+ #8
[ 0.371256] Hardware name: innotek gmb_h virtual_box/virtual_box, BIOS
virtual_box 12/01/2006
[ 0.372000] Call Trace:
[ 0.372000] ? dump_stack+0x5c/0x81
[ 0.372000] ? kmem_cache_destroy+0x1aa/0x1c0
[ 0.372000] ? acpi_sleep_proc_init+0x27/0x27
[ 0.372000] ? acpi_os_delete_cache+0xa/0x10
[ 0.372000] ? acpi_ut_delete_caches+0x56/0x7b
[ 0.372000] ? acpi_terminate+0xa/0x14
[ 0.372000] ? acpi_init+0x2af/0x34f
[ 0.372000] ? __class_create+0x4c/0x80
[ 0.372000] ? video_setup+0x7f/0x7f
[ 0.372000] ? acpi_sleep_proc_init+0x27/0x27
[ 0.372000] ? do_one_initcall+0x4e/0x1a0
[ 0.372000] ? kernel_init_freeable+0x189/0x20a
[ 0.372000] ? rest_init+0xc0/0xc0
[ 0.372000] ? kernel_init+0xa/0x100
[ 0.372000] ? ret_from_fork+0x25/0x30
[ 0.388039] kmem_cache_destroy Acpi-parse_ext: Slab cache still has objects
[ 0.389063] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W
4.12.0-rc4-next-20170608+ #8
[ 0.390557] Hardware name: innotek gmb_h virtual_box/virtual_box, BIOS
virtual_box 12/01/2006
[ 0.392000] Call Trace:
[ 0.392000] ? dump_stack+0x5c/0x81
[ 0.392000] ? kmem_cache_destroy+0x1aa/0x1c0
[ 0.392000] ? acpi_sleep_proc_init+0x27/0x27
[ 0.392000] ? acpi_os_delete_cache+0xa/0x10
[ 0.392000] ? acpi_ut_delete_caches+0x6d/0x7b
[ 0.392000] ? acpi_terminate+0xa/0x14
[ 0.392000] ? acpi_init+0x2af/0x34f
[ 0.392000] ? __class_create+0x4c/0x80
[ 0.392000] ? video_setup+0x7f/0x7f
[ 0.392000] ? acpi_sleep_proc_init+0x27/0x27
[ 0.392000] ? do_one_initcall+0x4e/0x1a0
[ 0.392000] ? kernel_init_freeable+0x189/0x20a
[ 0.392000] ? rest_init+0xc0/0xc0
[ 0.392000] ? kernel_init+0xa/0x100
[ 0.392000] ? 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_ut_delete_caches() function to delete local caches (acpi_gbl_namespace_
cache, state_cache, operand_cache, ps_node_cache, ps_node_ext_cache).
But the deletion codes in acpi_ut_delete_caches() function only delete
slab caches using kmem_cache_destroy() function, therefore the cache
objects should be flushed before acpi_ut_delete_caches() function.
"Acpi-Parse" cache and "Acpi-ParseExt" cache are used in an AML parse
function, acpi_ps_parse_loop(). The function should complete all ops
using acpi_ps_complete_final_op() when an error occurs due to invalid
AML codes.
However, the current implementation of acpi_ps_complete_final_op() does not
complete all ops when it meets some errors and this cause cache leak.
This cache leak has a security threat because an old kernel (<= 4.9) shows
memory locations of kernel functions in stack dump. Some malicious users
could use this information to neutralize kernel ASLR.
To fix ACPI cache leak for enhancing security, I made a patch to complete all
ops unconditionally for acpi_ps_complete_final_op() function.
I hope that this patch improves the security of Linux kernel.
Thank you.
Link:
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