On Fri, 2018-12-07 at 09:50 -0500, Waiman Long wrote: > On 12/07/2018 05:21 AM, Peter Zijlstra wrote: > > On Thu, Dec 06, 2018 at 05:11:40PM -0800, Bart Van Assche wrote: > > > The next patch in this series uses the class name in code that > > > detects calls to lock_acquire() while a class key is being freed. Hence > > > retain the class name for lock classes that are being freed. > > > > From readin the discussion with v2; you meant to say: 'uses the class > > name pointer', right? You're not actually ever going to dereference it, > > since that would be a UaF. > > > > > Cc: Peter Zijlstra <pet...@infradead.org> > > > Cc: Waiman Long <long...@redhat.com> > > > Cc: Johannes Berg <johan...@sipsolutions.net> > > > Signed-off-by: Bart Van Assche <bvanass...@acm.org> > > > --- > > > kernel/locking/lockdep.c | 4 +--- > > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > > index ecd92969674c..92bdb187987f 100644 > > > --- a/kernel/locking/lockdep.c > > > +++ b/kernel/locking/lockdep.c > > > @@ -4147,10 +4147,8 @@ static void zap_class(struct lock_class *class) > > > * Unhash the class and remove it from the all_lock_classes list: > > > */ > > > hlist_del_rcu(&class->hash_entry); > > > + class->hash_entry.pprev = NULL; > > > list_del(&class->lock_entry); > > > - > > > - RCU_INIT_POINTER(class->key, NULL); > > > - RCU_INIT_POINTER(class->name, NULL); > > > } > > > > > > static inline int within(const void *addr, void *start, unsigned long > > > size) > > > -- > > > 2.20.0.rc2.403.gdbc3b29805-goog > > > > > I still prefer keeping the clearing statements. Leaving key behind > should be OK as it is just a long value to be compared against. The > variable name is a different story as it is a pointer that will > reference bytes that it points to unless you save the name in a safe > storage area and change the pointer to point there.
I will drop this patch and update later patches accordingly. Bart.
