On Wed, Mar 17, 2021 at 09:47:40AM +0100, Marco Elver wrote: > Because memblock allocations are registered with kmemleak, the KFENCE > pool was seen by kmemleak as one large object. Later allocations through > kfence_alloc() that were registered with kmemleak via > slab_post_alloc_hook() would then overlap and trigger a warning. > Therefore, once the pool is initialized, we can remove (free) it from > kmemleak again, since it should be treated as allocator-internal and be > seen as "free memory". > > The second problem is that kmemleak is passed the rounded size, and not > the originally requested size, which is also the size of KFENCE objects. > To avoid kmemleak scanning past the end of an object and trigger a > KFENCE out-of-bounds error, fix the size if it is a KFENCE object. > > For simplicity, to avoid a call to kfence_ksize() in > slab_post_alloc_hook() (and avoid new IS_ENABLED(CONFIG_DEBUG_KMEMLEAK) > guard), just call kfence_ksize() in mm/kmemleak.c:create_object(). > > Reported-by: Luis Henriques <lhenriques@xxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Tested-by: Luis Henriques <lhenriques@xxxxxxx> > --- > mm/kfence/core.c | 9 +++++++++ > mm/kmemleak.c | 3 ++- > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index f7106f28443d..768dbd58170d 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -12,6 +12,7 @@ > #include <linux/debugfs.h> > #include <linux/kcsan-checks.h> > #include <linux/kfence.h> > +#include <linux/kmemleak.h> > #include <linux/list.h> > #include <linux/lockdep.h> > #include <linux/memblock.h> > @@ -481,6 +482,14 @@ static bool __init kfence_init_pool(void) > addr += 2 * PAGE_SIZE; > } > > + /* > + * The pool is live and will never be deallocated from this point on. > + * Remove the pool object from the kmemleak object tree, as it would > + * otherwise overlap with allocations returned by kfence_alloc(), which > + * are registered with kmemleak through the slab post-alloc hook. > + */ > + kmemleak_free(__kfence_pool); > + > return true; > > err: > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index c0014d3b91c1..fe6e3ae8e8c6 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -97,6 +97,7 @@ > #include <linux/atomic.h> > > #include <linux/kasan.h> > +#include <linux/kfence.h> > #include <linux/kmemleak.h> > #include <linux/memory_hotplug.h> > > @@ -589,7 +590,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, > atomic_set(&object->use_count, 1); > object->flags = OBJECT_ALLOCATED; > object->pointer = ptr; > - object->size = size; > + object->size = kfence_ksize((void *)ptr) ?: size; > object->excess_ref = 0; > object->min_count = min_count; > object->count = 0; /* white color initially */ > -- > 2.31.0.rc2.261.g7f71774620-goog >
