[PATCH v2] regmap: fix NULL pointer dereference in regmap_name_read_file()

From: David Lechner
Date: Mon Feb 19 2018 - 16:43:39 EST


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@xxxxxxxxxxxxxx>
---

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