Re: [PATCH 2/3] drm/sysfs: Grab lock for edid/modes_show

Re: [PATCH 2/3] drm/sysfs: Grab lock for edid/modes_show

[Julia Lawall]

Maybe line 294 should become an unlock and should be moved under 295?

julia

On Tue, 29 Sep 2015, kbuild test robot wrote:

> CC: kbuild-all@01.org
> In-Reply-To: <1443513993-5228-2-git-send-email-daniel.vetter@ffwll.ch>
> TO: Daniel Vetter <daniel.vetter@ffwll.ch>
> CC: DRI Development <dri-devel@lists.freedesktop.org>
> CC: Daniel Vetter <daniel.vetter@ffwll.ch>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>
>
> Hi Daniel,
>
> [auto build test results on v4.3-rc3 -- if it's inappropriate base, please ignore]
>
> :::::: branch date: 2 hours ago
> :::::: commit date: 2 hours ago
>
> >> drivers/gpu/drm/drm_sysfs.c:277:1-11: second lock on line 294
> --
> >> drivers/gpu/drm/drm_sysfs.c:297:1-7: preceding lock on line 277
>
> git remote add linux-review https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git remote update linux-review
> git checkout 0a4b5f2c3380cb718d25f3ecf7af6cbbc4a7bced
> vim +277 drivers/gpu/drm/drm_sysfs.c
>
> f453ba04 Dave Airlie   2008-11-07  271  	struct device *connector_dev = container_of(kobj, struct device, kobj);
> f453ba04 Dave Airlie   2008-11-07  272  	struct drm_connector *connector = to_drm_connector(connector_dev);
> f453ba04 Dave Airlie   2008-11-07  273  	unsigned char *edid;
> f453ba04 Dave Airlie   2008-11-07  274  	size_t size;
> 0a4b5f2c Daniel Vetter 2015-09-29  275  	ssize_t ret = 0;
> f453ba04 Dave Airlie   2008-11-07  276
> 0a4b5f2c Daniel Vetter 2015-09-29 @277  	mutex_lock(&connector->dev->mode_config.mutex);
> f453ba04 Dave Airlie   2008-11-07  278  	if (!connector->edid_blob_ptr)
> 0a4b5f2c Daniel Vetter 2015-09-29  279  		goto unlock;
> f453ba04 Dave Airlie   2008-11-07  280
> f453ba04 Dave Airlie   2008-11-07  281  	edid = connector->edid_blob_ptr->data;
> f453ba04 Dave Airlie   2008-11-07  282  	size = connector->edid_blob_ptr->length;
> f453ba04 Dave Airlie   2008-11-07  283  	if (!edid)
> 0a4b5f2c Daniel Vetter 2015-09-29  284  		goto unlock;
> f453ba04 Dave Airlie   2008-11-07  285
> f453ba04 Dave Airlie   2008-11-07  286  	if (off >= size)
> 0a4b5f2c Daniel Vetter 2015-09-29  287  		goto unlock;
> f453ba04 Dave Airlie   2008-11-07  288
> f453ba04 Dave Airlie   2008-11-07  289  	if (off + count > size)
> f453ba04 Dave Airlie   2008-11-07  290  		count = size - off;
> f453ba04 Dave Airlie   2008-11-07  291  	memcpy(buf, edid + off, count);
> f453ba04 Dave Airlie   2008-11-07  292
> 0a4b5f2c Daniel Vetter 2015-09-29  293  	ret = count;
> 0a4b5f2c Daniel Vetter 2015-09-29 @294  	mutex_lock(&connector->dev->mode_config.mutex);
> 0a4b5f2c Daniel Vetter 2015-09-29  295  unlock:
> 0a4b5f2c Daniel Vetter 2015-09-29  296
> 0a4b5f2c Daniel Vetter 2015-09-29 @297  	return ret;
> f453ba04 Dave Airlie   2008-11-07  298  }
> f453ba04 Dave Airlie   2008-11-07  299
> f453ba04 Dave Airlie   2008-11-07  300  static ssize_t modes_show(struct device *device,
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
>
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[PATCH 2/3] drm/sysfs: Grab lock for edid/modes_show

[Daniel Vetter]

We chase pointers/lists without taking the locks protecting them,
which isn't that good.

Fix it.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_sysfs.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 7506de0a75b4..d55e0d7a610d 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -261,23 +261,29 @@ static ssize_t edid_show(struct file *filp, struct kobject *kobj,
 	struct drm_connector *connector = to_drm_connector(connector_dev);
 	unsigned char *edid;
 	size_t size;
+	ssize_t ret = 0;
 
+	mutex_lock(&connector->dev->mode_config.mutex);
 	if (!connector->edid_blob_ptr)
-		return 0;
+		goto unlock;
 
 	edid = connector->edid_blob_ptr->data;
 	size = connector->edid_blob_ptr->length;
 	if (!edid)
-		return 0;
+		goto unlock;
 
 	if (off >= size)
-		return 0;
+		goto unlock;
 
 	if (off + count > size)
 		count = size - off;
 	memcpy(buf, edid + off, count);
 
-	return count;
+	ret = count;
+	mutex_lock(&connector->dev->mode_config.mutex);
+unlock:
+
+	return ret;
 }
 
 static ssize_t modes_show(struct device *device,
@@ -288,10 +294,12 @@ static ssize_t modes_show(struct device *device,
 	struct drm_display_mode *mode;
 	int written = 0;
 
+	mutex_lock(&connector->dev->mode_config.mutex);
 	list_for_each_entry(mode, &connector->modes, head) {
 		written += snprintf(buf + written, PAGE_SIZE - written, "%s\n",
 				    mode->name);
 	}
+	mutex_unlock(&connector->dev->mode_config.mutex);
 
 	return written;
 }
-- 
2.5.1

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