On Tue, 16 Jun 2020 11:43:11 -0400 Waiman Long <longman@xxxxxxxxxx> wrote: > As said by Linus: > > A symmetric naming is only helpful if it implies symmetries in use. > Otherwise it's actively misleading. > > In "kzalloc()", the z is meaningful and an important part of what the > caller wants. > > In "kzfree()", the z is actively detrimental, because maybe in the > future we really _might_ want to use that "memfill(0xdeadbeef)" or > something. The "zero" part of the interface isn't even _relevant_. > > The main reason that kzfree() exists is to clear sensitive information > that should not be leaked to other future users of the same memory > objects. > > Rename kzfree() to kfree_sensitive() to follow the example of the > recently added kvfree_sensitive() and make the intention of the API > more explicit. In addition, memzero_explicit() is used to clear the > memory to make sure that it won't get optimized away by the compiler. > > The renaming is done by using the command sequence: > > git grep -w --name-only kzfree |\ > xargs sed -i 's/\bkzfree\b/kfree_sensitive/' > > followed by some editing of the kfree_sensitive() kerneldoc and adding > a kzfree backward compatibility macro in slab.h. > > ... > > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -186,10 +186,12 @@ void memcg_deactivate_kmem_caches(struct mem_cgroup *, struct mem_cgroup *); > */ > void * __must_check krealloc(const void *, size_t, gfp_t); > void kfree(const void *); > -void kzfree(const void *); > +void kfree_sensitive(const void *); > size_t __ksize(const void *); > size_t ksize(const void *); > > +#define kzfree(x) kfree_sensitive(x) /* For backward compatibility */ > + What was the thinking here? Is this really necessary? I suppose we could keep this around for a while to ease migration. But not for too long, please.
