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

["Rafael J. Wysocki" <rafael@kernel.org>]

On Thu, Dec 1, 2016 at 12:10 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 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) {}
> --

Looks OK to me.

Whom do you expect to apply this?

Thanks,
Rafael