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

[arvind]

Hi,

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);

                kfree(name);
.
.
.
}

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.

~arvind