On Thu, Aug 09, 2018 at 03:51:55PM +0300, Dan Carpenter wrote:
> On Thu, Aug 09, 2018 at 02:13:24PM +0200, Greg KH wrote:
> > On Thu, Aug 09, 2018 at 01:43:58PM +0300, Dan Carpenter wrote:
> > > On Thu, Aug 09, 2018 at 01:08:38PM +0300, Dan Carpenter wrote:
> > > > On Thu, Aug 09, 2018 at 12:13:06PM +0530, Ajay Singh wrote:
> > > > > wilc_dir = debugfs_create_dir("wilc_wifi", NULL);
> > > > > - for (i = 0; i < ARRAY_SIZE(debugfs_info); i++) {
> > > > > - info = &debugfs_info[i];
> > > > > - debugfs_create_file(info->name,
> > > > > - info->perm,
> > > > > - wilc_dir,
> > > > > - &info->data,
> > > > > - &info->fops);
> > > > > + if (IS_ERR_OR_NULL(wilc_dir)) {
> > > > > + pr_err("Error creating debugfs\n");
> > > > > + return -EFAULT;
> > > > > }
> > > >
> > > > Just check for NULL. If someone builds without debugfs enabled in their
> > > > .config, that's their choice. No need to print a warning.
> > > >
> > >
> > > Reading it again, I'm not sure my email was clear... Just do this:
> > >
> > > wilc_dir = debugfs_create_dir("wilc_wifi", NULL);
> > > if (!wilc_dir)) {
> > > pr_err("Error creating debugfs/wilc_wifi/\n");
> > > return;
> > > }
> > >
> > > If debugfs_create_dir() returns an error pointer it means all the other
> > > debugfs functions are also just no-op stub functions. Passing an error
> > > pointer to them is harmless.
> >
> > No, please never care about the return value of a debugfs call, it
> > should never cause your code flow to do anything different. THis should
> > just be:
> > wilc_dir = debugfs_create_dir("wilc_wifi", NULL);
> > and then keep on going. You can always pass the return value of a
> > debugfs call to another one, no need to check anything.
> >
> > I've done a large sweep of the kernel tree for most of this pattern for
> > 4.18, and will keep doing it over time, as it keeps creeping back.
>
> Yeah, that's how I thought it was supposed be but then the cleanup
> doesn't work. We end up putting all the new debugfs files in the base
> debugsf directory. Doesn't it lead to a use after free if we unload the
> module?
If the creation of a directory fails, then almost always the creation of
files will also fail, so no real problem here as your system is really
hosed at that point in time. :)
thanks,
greg k-h
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