[PATCH] platform/x86: thinkpad_acpi: initialize tp_nvram_state variable

[PATCH] platform/x86: thinkpad_acpi: initialize tp_nvram_state variable

[trix]

From: Tom Rix <trix@redhat.com>

clang static analysis flags this represenative problem
thinkpad_acpi.c:2523:7: warning: Branch condition evaluates
  to a garbage value
                if (!oldn->mute ||
                    ^~~~~~~~~~~

In hotkey_kthread() mute is conditionally set by hotkey_read_nvram()
but unconditionally checked by hotkey_compare_and_issue_event().
So the tp_nvram_state variable s[2] needs to be initialized.

Fixes: 01e88f25985d ("ACPI: thinkpad-acpi: add CMOS NVRAM polling for hot keys (v9)")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 drivers/platform/x86/thinkpad_acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 47925c319d7b..24da8b6872f2 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -2573,7 +2573,7 @@ static void hotkey_compare_and_issue_event(struct tp_nvram_state *oldn,
  */
 static int hotkey_kthread(void *data)
 {
-	struct tp_nvram_state s[2];
+	struct tp_nvram_state s[2] = { 0 };
 	u32 poll_mask, event_mask;
 	unsigned int si, so;
 	unsigned long t;
-- 
2.18.1

Re: [PATCH] platform/x86: thinkpad_acpi: initialize tp_nvram_state variable

[Hans de Goede]

Hi,

On 9/13/20 9:02 PM, trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis flags this represenative problem
> thinkpad_acpi.c:2523:7: warning: Branch condition evaluates
>    to a garbage value
>                  if (!oldn->mute ||
>                      ^~~~~~~~~~~
> 
> In hotkey_kthread() mute is conditionally set by hotkey_read_nvram()
> but unconditionally checked by hotkey_compare_and_issue_event().
> So the tp_nvram_state variable s[2] needs to be initialized.
> 
> Fixes: 01e88f25985d ("ACPI: thinkpad-acpi: add CMOS NVRAM polling for hot keys (v9)")

Looking at the code I do not think this can actually happen,
this can only happen if the poll_mask == 0 the first time
through the loop so s[1] does never gets initialized and then
the second time to the loop poll_mask != 0, but if poll_mask
changes then we hit:

                 mutex_lock(&hotkey_thread_data_mutex);
                 if (was_frozen || hotkey_config_change != change_detector) {
                         /* forget old state on thaw or config change */
                         si = so;
                         t = 0;
                         change_detector = hotkey_config_change;
                 }

Where we set si = so so then this can also not happen.

I can understand the static-analyzer warning about this, and fixing
that warning is good. But I doubt that this warrants a fixes tag.

So with the Fixes tag dropped this is:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>


> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>   drivers/platform/x86/thinkpad_acpi.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index 47925c319d7b..24da8b6872f2 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -2573,7 +2573,7 @@ static void hotkey_compare_and_issue_event(struct tp_nvram_state *oldn,
>    */
>   static int hotkey_kthread(void *data)
>   {
> -	struct tp_nvram_state s[2];
> +	struct tp_nvram_state s[2] = { 0 };
>   	u32 poll_mask, event_mask;
>   	unsigned int si, so;
>   	unsigned long t;
> 

Re: [PATCH] platform/x86: thinkpad_acpi: initialize tp_nvram_state variable

[mark gross]

Acked-by: mark gross <mgross@linux.intel.com>

--mark


On Sun, Sep 13, 2020 at 12:02:03PM -0700, trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis flags this represenative problem
> thinkpad_acpi.c:2523:7: warning: Branch condition evaluates
>   to a garbage value
>                 if (!oldn->mute ||
>                     ^~~~~~~~~~~
> 
> In hotkey_kthread() mute is conditionally set by hotkey_read_nvram()
> but unconditionally checked by hotkey_compare_and_issue_event().
> So the tp_nvram_state variable s[2] needs to be initialized.
> 
> Fixes: 01e88f25985d ("ACPI: thinkpad-acpi: add CMOS NVRAM polling for hot keys (v9)")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  drivers/platform/x86/thinkpad_acpi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index 47925c319d7b..24da8b6872f2 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -2573,7 +2573,7 @@ static void hotkey_compare_and_issue_event(struct tp_nvram_state *oldn,
>   */
>  static int hotkey_kthread(void *data)
>  {
> -	struct tp_nvram_state s[2];
> +	struct tp_nvram_state s[2] = { 0 };
>  	u32 poll_mask, event_mask;
>  	unsigned int si, so;
>  	unsigned long t;
> -- 
> 2.18.1
>