potential NULL dereference in sysfs_merge_group()

[Dan Carpenter <error27@gmail.com>]

Hi Alan,

There is a bug in sysfs_merge_group() where it doesn't handle a NULL
grp parameter properly.  The only caller in the kernel passes in a valid
grp pointer so it doesn't affect anything yet.

fs/sysfs/group.c +175 sysfs_merge_group(15)
	error: we previously assumed 'grp' could be null.
   168		if (grp)
                    ^^^
	assumes that grp can be NULL.

   169			dir_sd = sysfs_get_dirent(kobj->sd, NULL, grp->name);
   170		else
   171			dir_sd = sysfs_get(kobj->sd);
   172		if (!dir_sd)
   173			return -ENOENT;
   174	
   175		for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
                                    ^^^^^
	grp is dereferenced here.

   176			error = sysfs_add_file(dir_sd, *attr, SYSFS_KOBJ_ATTR);

I'm not sure how you want to handle this.

regards,
dan carpenter