linux-kernel - [PATCH v2] regmap: potentially duplicate the name string stored in regmap

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Date:   Wed, 13 Dec 2017 17:25:31 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: [PATCH v2] regmap: potentially duplicate the name string stored in regmap

Currently we just copy over the pointer passed to regmap_init() in
the regmap config struct. To be on the safe side: duplicate the string
with kstrdup_const() so that if an unaware user passes an address to
a stack-allocated buffer, we won't crash.

Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
---
v1 -> v2:
- drop the patches that were either applied or done by Mark
- fix an error path
- use kstrdup_const() instead of kstrdup() to avoid unnecessary memory
  allocations

 drivers/base/regmap/regmap.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 16a66ba84aef..bd62600b40e4 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -672,6 +672,14 @@ struct regmap *__regmap_init(struct device *dev,
 		goto err;
 	}
 
+	if (config->name) {
+		map->name = kstrdup_const(config->name, GFP_KERNEL);
+		if (!map->name) {
+			ret = -ENOMEM;
+			goto err_map;
+		}
+	}
+
 	if (config->disable_locking) {
 		map->lock = map->unlock = regmap_lock_unlock_none;
 	} else if (config->lock && config->unlock) {
@@ -682,7 +690,7 @@ struct regmap *__regmap_init(struct device *dev,
 		map->hwlock = hwspin_lock_request_specific(config->hwlock_id);
 		if (!map->hwlock) {
 			ret = -ENXIO;
-			goto err_map;
+			goto err_name;
 		}
 
 		switch (config->hwlock_mode) {
@@ -762,7 +770,6 @@ struct regmap *__regmap_init(struct device *dev,
 	map->volatile_reg = config->volatile_reg;
 	map->precious_reg = config->precious_reg;
 	map->cache_type = config->cache_type;
-	map->name = config->name;
 
 	spin_lock_init(&map->async_lock);
 	INIT_LIST_HEAD(&map->async_list);
@@ -1118,6 +1125,8 @@ struct regmap *__regmap_init(struct device *dev,
 err_hwlock:
 	if (map->hwlock)
 		hwspin_lock_free(map->hwlock);
+err_name:
+	kfree_const(map->name);
 err_map:
 	kfree(map);
 err:
@@ -1307,6 +1316,7 @@ void regmap_exit(struct regmap *map)
 	}
 	if (map->hwlock)
 		hwspin_lock_free(map->hwlock);
+	kfree_const(map->name);
 	kfree(map);
 }
 EXPORT_SYMBOL_GPL(regmap_exit);
-- 
2.15.1