Re: [PATCH v2 1/6] debugfs: fix automount d_fsdata usage

[Greg Kroah-Hartman]

On Sat, Nov 25, 2023 at 07:31:47PM +0100, Johannes Berg wrote:
> On Sat, 2023-11-25 at 14:48 +0000, Greg Kroah-Hartman wrote:
> > On Fri, Nov 24, 2023 at 05:25:24PM +0100, Johannes Berg wrote:
> > > From: Johannes Berg <johannes.berg@xxxxxxxxx>
> > > 
> > > debugfs_create_automount() stores a function pointer in d_fsdata,
> > > but since commit 7c8d469877b1 ("debugfs: add support for more
> > > elaborate ->d_fsdata") debugfs_release_dentry() will free it, now
> > > conditionally on DEBUGFS_FSDATA_IS_REAL_FOPS_BIT, but that's not
> > > set for the function pointer in automount. As a result, removing
> > > an automount dentry would attempt to free the function pointer.
> > > Luckily, the only user of this (tracing) never removes it.
> > > 
> > > Nevertheless, it's safer if we just handle the fsdata in one way,
> > > namely either DEBUGFS_FSDATA_IS_REAL_FOPS_BIT or allocated. Thus,
> > > change the automount to allocate it, and use the real_fops in the
> > > data to indicate whether or not automount is filled, rather than
> > > adding a type tag. At least for now this isn't actually needed,
> > > but the next changes will require it.
> > > 
> > > Also check in debugfs_file_get() that it gets only called
> > > on regular files, just to make things clearer.
> > > 
> > > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
> > > ---
> > > v2: add missing kfree() pointed out by smatch
> > 
> > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> I have to fix the Kconfig issue in one of the later (wireless) patches,
> but does that mean you'd actually prefer the debugfs changes go through
> the wireless tree, together with the code using it?

I'm all for you taking these through the wireless tree, have fun!

greg k-h