Re: [PATCH v1] sysfs: fix sysfs_kf_seq_show null pointer dereference

[Christoph Hellwig]

On Tue, Jun 14, 2022 at 07:28:31PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Jun 14, 2022 at 05:24:01PM +0000, Will McVicker wrote:
> > When the kobj->ktype is null,
> 
> How can that happen?  What in-tree code does that?

Yes, I'd be really curious how we arrived there.  I we ever end in
this case we're having a major problem, as all the sysfs files
should go through sysfs_add_file_mode_ns, which already derferences
kobj->ktype->sysfs_ops directly.  I.e. for this to happen
kobj->ktype must have been cleared on a live file, or someone
must have bypassed sysfs_add_file_mode_ns.