Just to get a sense of what's happening, report the number of NULL assignments that have been done. After booting an otherwise standard Ubuntu image, this shows about 240,000 NULLifications have been performed.
Signed-off-by: Kees Cook <[email protected]> --- Cc: Christoph Lameter <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: David Rientjes <[email protected]> Cc: Joonsoo Kim <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Hyeonggon Yoo <[email protected]> Cc: [email protected] --- include/linux/slab.h | 3 +++ mm/slab_common.c | 4 ++++ 2 files changed, 7 insertions(+) diff --git a/include/linux/slab.h b/include/linux/slab.h index 2717ad238fa2..a4740c8b6ccb 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -469,6 +469,8 @@ void __kfree(const void *objp); void __kfree_sensitive(const void *objp); size_t __ksize(const void *objp); +extern atomic_t count_nulled; + static inline void kfree_and_null(void **ptr) { __kfree(*ptr); @@ -487,6 +489,7 @@ static inline void kfree_sensitive_and_null(void **ptr) ({ \ typeof(x) *__ptr = &(x); \ __how ## _and_null((void **)__ptr); \ + atomic_inc(&count_nulled); \ }) #define __free_and_maybe_null(__how, x) \ __builtin_choose_expr(__is_lvalue(x), \ diff --git a/mm/slab_common.c b/mm/slab_common.c index 9a82952ec266..0412cbab81f9 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -42,6 +42,9 @@ LIST_HEAD(slab_caches); DEFINE_MUTEX(slab_mutex); struct kmem_cache *kmem_cache; +atomic_t count_nulled = ATOMIC_INIT(0); +EXPORT_SYMBOL(count_nulled); + /* * Set of flags that will prevent slab merging */ @@ -1084,6 +1087,7 @@ static void print_slabinfo_header(struct seq_file *m) * without _too_ many complaints. */ seq_puts(m, "slabinfo - version: 2.1\n"); + seq_printf(m, "# nulled: %d\n", atomic_read(&count_nulled)); seq_puts(m, "# name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>"); seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>"); seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>"); -- 2.34.1
