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 <david@xxxxxxxxxxxxxx>
> > ---
> >   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.