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

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On 9/13/20 9:02 PM, trix@xxxxxxxxxx wrote:
From: Tom Rix <trix@xxxxxxxxxx>

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:

                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@xxxxxxxxxx>

Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
  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;

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