On Mon, 11 Oct 2021, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, Oct 11, 2021 at 04:19:58PM +0200, Christian König wrote: >> > > > > And then throw it away, later, when you want to remove the directory, >> > > > > look it up with a call to debugfs_lookup() and pass that to >> > > > > debugfs_remove() (which does so recursively). >> > > > > >> > > > > There should never be a need to save, or check, the result of any >> > > > > debugfs call. If so, odds are it is being used incorrectly. >> > > Yeah, exactly that's the problem I see here. >> > > >> > > We save the return value because the DRM subsystem is creating a debugfs >> > > directory for the drivers to use. >> > That's fine for now, not a big deal. And even if there is an error, >> > again, you can always feed that error back into the debugfs subsystem on >> > another call and it will handle it correctly. >> >> Problem is it isn't, we have a crash because the member isn't a pointer but >> an ERR_PTR instead. > > Again, that is fine, you can feed that into debugfs and it will "just > work". Treat it as an opaque pointer, not a *dentry and you will be > fine. Hmm, some of the patches add things like: + + if (!root) + goto error; + minor->debugfs_root = debugfs_create_dir(name, root); Superficially this seems okay, as it looks like debugfs_create_dir() doesn't actually cope with NULL values. However, since ->debugfs_root comes from debugfs_create_dir() I presume it'll never be NULL on errors anyway but rather an error pointer! So I think we probably need to go through the drm subsystem and look for existing similar patterns in fix them. BR, Jani. > > thanks, > > greg k-h -- Jani Nikula, Intel Open Source Graphics Center
