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 <da...@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

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