linux-hardening - [PATCH][next] drm/i915: Fix -Wstringop-overflow warning in call to intel_read_wm

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Date:   Wed, 27 Apr 2022 17:53:01 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] drm/i915: Fix -Wstringop-overflow warning in call to
 intel_read_wm_latency()

Fix the following -Wstringop-overflow warnings when building with GCC-11:

drivers/gpu/drm/i915/intel_pm.c:3106:9: warning: ‘intel_read_wm_latency’ accessing 16 bytes in a region of size 10 [-Wstringop-overflow=]
 3106 |         intel_read_wm_latency(dev_priv, dev_priv->wm.pri_latency);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/intel_pm.c:3106:9: note: referencing argument 2 of type ‘u16 *’ {aka ‘short unsigned int *’}
drivers/gpu/drm/i915/intel_pm.c:2861:13: note: in a call to function ‘intel_read_wm_latency’
 2861 | static void intel_read_wm_latency(struct drm_i915_private *dev_priv,
      |             ^~~~~~~~~~~~~~~~~~~~~

by removing the over-specified array size from the argument declarations.

It seems that this code is actually safe because the size of the
array depends on the hardware generation, and the function checks
for that.

This helps with the ongoing efforts to globally enable
-Wstringop-overflow.

Link: https://github.com/KSPP/linux/issues/181
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/gpu/drm/i915/intel_pm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index ee0047fdc95d..5735915facc5 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2862,7 +2862,7 @@ static void ilk_compute_wm_level(const struct drm_i915_private *dev_priv,
 }
 
 static void intel_read_wm_latency(struct drm_i915_private *dev_priv,
-				  u16 wm[8])
+				  u16 wm[])
 {
 	struct intel_uncore *uncore = &dev_priv->uncore;
 
-- 
2.27.0