linux-kernel - [PATCH 1/2] drm: make drm_dev_set_unique() not use a format string

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Date:	Tue,  8 Dec 2015 23:12:11 +0100
From:	Nicolas Iooss <nicolas.iooss_linux@....org>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	David Airlie <airlied@...ux.ie>,
	Jianwei Wang <jianwei.wang.chn@...il.com>,
	Alison Wang <alison.wang@...escale.com>,
	Mark Yao <mark.yao@...k-chips.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Terje Bergström <tbergstrom@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Nicolas Iooss <nicolas.iooss_linux@....org>
Subject: [PATCH 1/2] drm: make drm_dev_set_unique() not use a format string

drm_dev_set_unique() uses a format string to define the unique name of a
device.  This feature is not used as currently all the calls to this
function either use "%s" as a format string or directly use
dev_name().

Even though this second kind of call does not introduce security
problems, because there cannot be "%" characters in dev_name() results,
gcc issues a warning when building with -Wformat-security flag
("warning: format string is not a string literal (potentially
insecure)").  This warning is useful to find real bugs like the one
fixed by commit 3958b79266b1 ("configfs: fix kernel infoleak through
user-controlled format string").  False positives which do not bring
an extra value make the work of finding real bugs harder.

Therefore remove the format-string feature from drm_dev_set_unique().

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
---
 drivers/gpu/drm/drm_drv.c                   | 11 +++--------
 drivers/gpu/drm/nouveau/nouveau_drm.c       |  2 +-
 drivers/gpu/drm/rockchip/rockchip_drm_drv.c |  2 +-
 include/drm/drmP.h                          |  2 +-
 4 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 7dd6728dd092..20eaa0aae205 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -797,7 +797,7 @@ EXPORT_SYMBOL(drm_dev_unregister);
 /**
  * drm_dev_set_unique - Set the unique name of a DRM device
  * @dev: device of which to set the unique name
- * @fmt: format string for unique name
+ * @name: unique name
  *
  * Sets the unique name of a DRM device using the specified format string and
  * a variable list of arguments. Drivers can use this at driver probe time if
@@ -805,15 +805,10 @@ EXPORT_SYMBOL(drm_dev_unregister);
  *
  * Return: 0 on success or a negative error code on failure.
  */
-int drm_dev_set_unique(struct drm_device *dev, const char *fmt, ...)
+int drm_dev_set_unique(struct drm_device *dev, const char *name)
 {
-	va_list ap;
-
 	kfree(dev->unique);
-
-	va_start(ap, fmt);
-	dev->unique = kvasprintf(GFP_KERNEL, fmt, ap);
-	va_end(ap);
+	dev->unique = kstrdup(name, GFP_KERNEL);
 
 	return dev->unique ? 0 : -ENOMEM;
 }
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 1d3ee5179ab8..2d23f95f17ce 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -1046,7 +1046,7 @@ nouveau_platform_device_create(const struct nvkm_device_tegra_func *func,
 		goto err_free;
 	}
 
-	err = drm_dev_set_unique(drm, "%s", dev_name(&pdev->dev));
+	err = drm_dev_set_unique(drm, dev_name(&pdev->dev));
 	if (err < 0)
 		goto err_free;
 
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index f22e1e1ee64a..215d6c44af55 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -450,7 +450,7 @@ static int rockchip_drm_bind(struct device *dev)
 	if (!drm)
 		return -ENOMEM;
 
-	ret = drm_dev_set_unique(drm, "%s", dev_name(dev));
+	ret = drm_dev_set_unique(drm, dev_name(dev));
 	if (ret)
 		goto err_free;
 
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 0a271ca1f7c7..f14c25a6bbf2 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1059,7 +1059,7 @@ void drm_dev_ref(struct drm_device *dev);
 void drm_dev_unref(struct drm_device *dev);
 int drm_dev_register(struct drm_device *dev, unsigned long flags);
 void drm_dev_unregister(struct drm_device *dev);
-int drm_dev_set_unique(struct drm_device *dev, const char *fmt, ...);
+int drm_dev_set_unique(struct drm_device *dev, const char *name);
 
 struct drm_minor *drm_minor_acquire(unsigned int minor_id);
 void drm_minor_release(struct drm_minor *minor);
-- 
2.6.3

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