Re: [PATCH] debugfs: Add check for module parameter name

From: arvind
Date: Thu Sep 21 2017 - 12:47:54 EST


On Thursday 21 September 2017 06:14 PM, Al Viro wrote:
On Thu, Sep 21, 2017 at 05:46:54PM +0530, Arvind Yadav wrote:
Here, start_creating() is calling by debugfs_create_dir()
and debugfs_create_automount(). driver can pass name as NULL in
debugfs_create_dir and debugfs_create_automount. So we need to
add check for 'name'.
Huh? "Driver can pass any kind of crap pointer when calling this
function, so let's check if that crap happens to be NULL and bail
out in that particular case"? Or am I misreading that?
Your are correct.

Do you have any in-tree examples, or is that about some out-of-tree
code that needs to be saved from itself?

Please check "drivers/base/power/opp/debugfs.c"

static bool opp_debug_create_supplies(struct dev_pm_opp *opp,
struct opp_table *opp_table,
struct dentry *pdentry)
struct dentry *d;
int i;
char *name;

for (i = 0; i < opp_table->regulator_count; i++) {
name = kasprintf(GFP_KERNEL, "supply-%d", i);

/* Create per-opp directory */
d = debugfs_create_dir(name, pdentry);


kasprintf() can fail here and It can return NULL.
In this case, We are passing NULL value to debugfs_create_dir().
I know, we will have to handle kasprintf() first instead of adding
NULL check in start_creating(). I have seen few driver where they have done
similar kind of implementation. Also I am adding check for kasprintf.