linux-kernel - [PATCH] i915: don't call drm_atomic_state

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Message-Id: <20161018151652.2690201-1-arnd@arndb.de>
Date:   Tue, 18 Oct 2016 17:16:23 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Imre Deak <imre.deak@...el.com>,
        Ander Conselvan de Oliveira 
        <ander.conselvan.de.oliveira@...el.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] i915: don't call drm_atomic_state_put on invalid pointer

The introduction of reference counting on the state structures caused
sanitize_watermarks() in i915 to break in the error handling case,
as pointed out by gcc -Wmaybe-uninitialized

drivers/gpu/drm/i915/intel_display.c: In function ‘intel_modeset_init’:
include/drm/drm_atomic.h:224:2: error: ‘state’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

This changes the function back to only drop the reference count
when it was successfully allocated first.

Fixes: 0853695c3ba4 ("drm: Add reference counting to drm_atomic_state")
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/i915/intel_display.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6d168685bbda..6a26da143aa6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -16314,7 +16314,7 @@ static void sanitize_watermarks(struct drm_device *dev)
 		 * BIOS-programmed watermarks untouched and hope for the best.
 		 */
 		WARN(true, "Could not determine valid watermarks for inherited state\n");
-		goto fail;
+		goto put_state;
 	}
 
 	/* Write calculated watermark values back */
@@ -16325,8 +16325,9 @@ static void sanitize_watermarks(struct drm_device *dev)
 		dev_priv->display.optimize_watermarks(cs);
 	}
 
-fail:
+put_state:
 	drm_atomic_state_put(state);
+fail:
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 }
-- 
2.9.0