[PATCH v3] platform/x86: intel_telemetry: initialize default trace verbosity

[Aleksandrova Alyona]

telemetry_def_get_trace_verbosity() returns success without initializing
the output verbosity value.

The default telemetry operations are installed when the core driver is
initialized and again by telemetry_clear_pltdata() when the platform
driver is removed. The telemetry debugfs files can remain available after
the platform driver removal.

A subsequent read of pss_trace_verbosity or ioss_trace_verbosity calls
telemetry_get_trace_verbosity(), which may use the default callback and
return success without setting verbosity. The uninitialized value is then
passed to seq_printf().

Validate the output pointer and initialize the default verbosity to zero
so callers never use an uninitialized value after a successful call.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 378f956e3f93 ("platform/x86: Add Intel Telemetry Core Driver")
Signed-off-by: Aleksandrova Alyona <aga@xxxxxxxxxx>
---
v3: Add the missing revision history as requested by Ilpo Järvinen.

v2: Rebase onto the current master branch and update the file path after
Intel telemetry was moved to drivers/platform/x86/intel/telemetry/core.c.

 drivers/platform/x86/intel/telemetry/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/platform/x86/intel/telemetry/core.c b/drivers/platform/x86/intel/telemetry/core.c
index f312864b8d07a..62299524a07b2 100644
--- a/drivers/platform/x86/intel/telemetry/core.c
+++ b/drivers/platform/x86/intel/telemetry/core.c
@@ -24,6 +24,10 @@ static struct telemetry_core_config telm_core_conf;
 static int telemetry_def_get_trace_verbosity(enum telemetry_unit telem_unit,
 					     u32 *verbosity)
 {
+	if (!verbosity)
+		return -EINVAL;
+
+	*verbosity = 0;
 	return 0;
 }
 
-- 
2.26.2