Re: [PATCH 1/2] regmap: fix NULL pointer dereference in regmap_name_read_file()

[David Lechner]

On 01/24/2018 10:14 AM, Lars-Peter Clausen wrote:

On 01/23/2018 11:53 PM, David Lechner wrote:

This fixes a possible NULL pointer dereference oops in
regmap_name_read_file() when the regmap does not have a device
associated with it.

Signed-off-by: David Lechner <da...@lechnology.com>
---
  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 36ce351..0df7379 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 = NULL;
        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);

Won't this print "(null)" now? Not sure if that is the best approach.

The commit adding regmap_name_read_file() just says:

        regmap: Expose the driver name in debugfs

        Add a file called 'name' containing the name of the driver.

So, if a regmap doesn't have a driver, then "(null)" seems OK to me.
This is just for debugging anyway.