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If registration fails, ChainPinInit drops the >>> already initialized Subsystem. Its PinnedDrop currently calls >>> configfs_unregister_subsystem() unconditionally. >>> >>> configfs_unregister_subsystem() requires registration to have completed >>> and immediately dereferences the subsystem dentry. Registering a >>> duplicate subsystem name returns -EEXIST before installing that dentry, >>> so the cleanup path dereferences NULL and panics the kernel. >>> >>> Track successful registration explicitly and only unregister in that >>> state. Keep mutex destruction unconditional because it is initialized >>> before registration. >>> >>> Fixes: 446cafc295bf ("rust: configfs: introduce rust support for config= fs") >>> Signed-off-by: Younes Akhouayri >>> --- >>> rust/kernel/configfs.rs | 14 ++++++++++---- >>> 1 file changed, 10 insertions(+), 4 deletions(-) >>> >>> diff --git a/rust/kernel/configfs.rs b/rust/kernel/configfs.rs >>> index cd082b83e9e7..f358e227ce09 100644 >>> --- a/rust/kernel/configfs.rs >>> +++ b/rust/kernel/configfs.rs >>> @@ -130,6 +130,7 @@ pub struct Subsystem { >>> subsystem: Opaque, >>> #[pin] >>> data: Data, >>> + registered: bool, >> >> No flag just for destruction. Please change new logic to avoid needing t= his. > > I guess we can have a local `UnregisteredSubsystem` that we can > cast to a `Subsystem` once registration succeeds. Is that what you have > in mind? You can use the arbitrary code block feature of pin-init to run code before arming the destructor: _: { let result =3D crate::error::to_result( unsafe { bindings::configfs_register_subsystem(subsystem.get())= } ); if let Err(err) =3D result { unsafe { bindings::mutex_destroy(&raw mut (*subsystem.get()).su= _mutex) }; } result? } That said, why is the configfs not initializer the mutex, but rather users = do? Best, Gary