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From:   David Lechner <david@lechnology.com>
To:     linux-kernel@vger.kernel.org
Cc:     David Lechner <david@lechnology.com>,
        Mark Brown <broonie@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH v2] regmap: fix NULL pointer dereference in regmap_name_read_file()
Date:   Mon, 19 Feb 2018 15:43:01 -0600
Message-Id: <1519076582-7687-2-git-send-email-david@lechnology.com>
In-Reply-To: <1519076582-7687-1-git-send-email-david@lechnology.com>
References: <1519076582-7687-1-git-send-email-david@lechnology.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This fixes a possible NULL pointer dereference oops in
regmap_name_read_file() when the regmap does not have a device
associated with it. For example syscon regmaps retrieved with
syscon_regmap_lookup_by_compatible() don't have a device.

Signed-off-by: David Lechner <david@lechnology.com>
---

v2 changes:
- point out case where this can actually happen in the commit message
- print "nodev" instead of "(null)" if there is no device

 drivers/base/regmap/regmap-debugfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index f326633..7eb512b 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -40,6 +40,7 @@ static ssize_t regmap_name_read_file(struct file *file,
 				     loff_t *ppos)
 {
 	struct regmap *map = file->private_data;
+	const char *name = "nodev";
 	int ret;
 	char *buf;
 
@@ -47,7 +48,10 @@ static ssize_t regmap_name_read_file(struct file *file,
 	if (!buf)
 		return -ENOMEM;
 
-	ret = snprintf(buf, PAGE_SIZE, "%s\n", map->dev->driver->name);
+	if (map->dev && map->dev->driver)
+		name = map->dev->driver->name;
+
+	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 	if (ret < 0) {
 		kfree(buf);
 		return ret;
-- 
2.7.4