[PATCH v2] x86/suspend: fix false positive KASAN warning on suspend/resume

Josh Poimboeuf
2016-12-01T20:32:01Z

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
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 later false
positive warnings like the one above.

Reported-by: Scott Bauer <scott.bauer@intel.com>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/acpi/wakeup_64.S | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index 169963f..1df9b75 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -109,6 +109,22 @@ ENTRY(do_suspend_lowlevel)
movq pt_regs_r14(%rax), %r14
movq pt_regs_r15(%rax), %r15

+#ifdef CONFIG_KASAN
+ /*
+ * The suspend path may have poisoned some areas deeper in the stack,
+ * which we now need to unpoison.
+ *
+ * We can't call kasan_unpoison_task_stack_below() because it uses %gs
+ * for 'current', which hasn't been set up yet. Instead, calculate the
+ * stack range manually and call kasan_unpoison_shadow().
+ */
+ movq %rsp, %rdi
+ andq $CURRENT_MASK, %rdi
+ movq %rsp, %rsi
+ xorq %rdi, %rsi
+ call kasan_unpoison_shadow
+#endif
+
xorl %eax, %eax
addq $8, %rsp
FRAME_END
--
2.7.4