[PATCH] x86/suspend: fix false positive KASAN warning on suspend/resume

Josh Poimboeuf
2016-11-30T23:10:17Z

Resuming from a suspend operation is showing a KASAN false positive
warning:

BUG: KASAN: stack-out-of-bounds in unwind_get_return_address+0x11d/0x130 at addr ffff8803867d7878
Read of size 8 by task pm-suspend/7774
page:ffffea000e19f5c0 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x2ffff0000000000()
page dumped because: kasan: bad access detected
CPU: 0 PID: 7774 Comm: pm-suspend Tainted: G B 4.9.0-rc7+ #8
Hardware name: Gigabyte Technology Co., Ltd. Z170X-UD5/Z170X-UD5-CF, BIOS F5 03/07/2016
ffff8803867d7468 ffffffffb4c0d051 ffff8803867d7500 ffff8803867d7878
ffff8803867d74f0 ffffffffb45cbe34 ffffffffb4e64136 ffffffffb4510d42
ffff8803828c3f4c 0000000000000097 0000000041b58ab3 ffffffffb6192731
Call Trace:
dump_stack+0x63/0x82
kasan_report_error+0x4b4/0x4e0
? acpi_hw_read_port+0xd0/0x1ea
? kfree_const+0x22/0x30
? acpi_hw_validate_io_request+0x1a6/0x1a6
__asan_report_load8_noabort+0x61/0x70
? unwind_get_return_address+0x11d/0x130
unwind_get_return_address+0x11d/0x130
? unwind_next_frame+0x97/0xf0
__save_stack_trace+0x92/0x100
save_stack_trace+0x1b/0x20
save_stack+0x46/0xd0
? save_stack_trace+0x1b/0x20
? save_stack+0x46/0xd0
? kasan_kmalloc+0xad/0xe0
? kasan_slab_alloc+0x12/0x20
? acpi_hw_read+0x2b6/0x3aa
? acpi_hw_validate_register+0x20b/0x20b
? acpi_hw_write_port+0x72/0xc7
? acpi_hw_write+0x11f/0x15f
? acpi_hw_read_multiple+0x19f/0x19f
? memcpy+0x45/0x50
? acpi_hw_write_port+0x72/0xc7
? acpi_hw_write+0x11f/0x15f
? acpi_hw_read_multiple+0x19f/0x19f
? kasan_unpoison_shadow+0x36/0x50
kasan_kmalloc+0xad/0xe0
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc_trace+0xbc/0x1e0
? acpi_get_sleep_type_data+0x9a/0x578
acpi_get_sleep_type_data+0x9a/0x578
acpi_hw_legacy_wake_prep+0x88/0x22c
? acpi_hw_legacy_sleep+0x3c7/0x3c7
? acpi_write_bit_register+0x28d/0x2d3
? acpi_read_bit_register+0x19b/0x19b
acpi_hw_sleep_dispatch+0xb5/0xba
acpi_leave_sleep_state_prep+0x17/0x19
acpi_suspend_enter+0x154/0x1e0
? trace_suspend_resume+0xe8/0xe8
suspend_devices_and_enter+0xb09/0xdb0
? printk+0xa8/0xd8
? arch_suspend_enable_irqs+0x20/0x20
? try_to_freeze_tasks+0x295/0x600
pm_suspend+0x6c9/0x780
? finish_wait+0x1f0/0x1f0
? suspend_devices_and_enter+0xdb0/0xdb0
state_store+0xa2/0x120
? kobj_attr_show+0x60/0x60
kobj_attr_store+0x36/0x70
sysfs_kf_write+0x131/0x200
kernfs_fop_write+0x295/0x3f0
__vfs_write+0xef/0x760
? handle_mm_fault+0x1346/0x35e0
? do_iter_readv_writev+0x660/0x660
? __pmd_alloc+0x310/0x310
? do_lock_file_wait+0x1e0/0x1e0
? apparmor_file_permission+0x18/0x20
? security_file_permission+0x73/0x1c0
? rw_verify_area+0xbd/0x2b0
vfs_write+0x149/0x4a0
SyS_write+0xd9/0x1c0
? SyS_read+0x1c0/0x1c0
entry_SYSCALL_64_fastpath+0x1e/0xad
Memory state around the buggy address:
ffff8803867d7700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8803867d7780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8803867d7800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f4
^
ffff8803867d7880: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
ffff8803867d7900: 00 00 00 f1 f1 f1 f1 04 f4 f4 f4 f3 f3 f3 f3 00

KASAN instrumentation poisons the stack when entering a function and
unpoisons it when exiting the function. However, in the suspend path,
some functions never return, so their stack never gets unpoisoned,
resulting in stale KASAN shadow data which can cause false positive
warnings like the one above.

Reported-by: Scott Bauer <scott.bauer@intel.com>
Tested-by: Scott Bauer <scott.bauer@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/acpi/sleep.c | 3 +++
include/linux/kasan.h | 7 +++++++
2 files changed, 10 insertions(+)

diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 4858733..62bd046 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -115,6 +115,9 @@ int x86_acpi_suspend_lowlevel(void)
pause_graph_tracing();
do_suspend_lowlevel();
unpause_graph_tracing();
+
+ kasan_unpoison_stack_below_sp();
+
return 0;
}

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 820c0ad..e0945d5 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -45,6 +45,12 @@ void kasan_unpoison_shadow(const void *address, size_t size);

void kasan_unpoison_task_stack(struct task_struct *task);
void kasan_unpoison_stack_above_sp_to(const void *watermark);
+asmlinkage void kasan_unpoison_task_stack_below(const void *watermark);
+
+static inline void kasan_unpoison_stack_below_sp(void)
+{
+ kasan_unpoison_task_stack_below(__builtin_frame_address(0));
+}

void kasan_alloc_pages(struct page *page, unsigned int order);
void kasan_free_pages(struct page *page, unsigned int order);
@@ -87,6 +93,7 @@ static inline void kasan_unpoison_shadow(const void *address, size_t size) {}

static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
static inline void kasan_unpoison_stack_above_sp_to(const void *watermark) {}
+static inline void kasan_unpoison_stack_below_sp(void) {}

static inline void kasan_enable_current(void) {}
static inline void kasan_disable_current(void) {}
--
2.7.4