From: Marco Elver <elver@xxxxxxxxxx> Subject: kfence: make compatible with kmemleak 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(). Link: https://lkml.kernel.org/r/20210317084740.3099921-1-elver@xxxxxxxxxx Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Reported-by: Luis Henriques <lhenriques@xxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> Tested-by: Luis Henriques <lhenriques@xxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kfence/core.c | 9 +++++++++ mm/kmemleak.c | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) --- a/mm/kfence/core.c~kfence-make-compatible-with-kmemleak +++ a/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> @@ -480,6 +481,14 @@ 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: --- a/mm/kmemleak.c~kfence-make-compatible-with-kmemleak +++ a/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_ob 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 */ _
