From: William Kucharski <william.kucharski@xxxxxxxxxx> Subject: mm: ksize() should silently accept a NULL pointer Other mm routines such as kfree() and kzfree() silently do the right thing if passed a NULL pointer, so ksize() should do the same. Link: http://lkml.kernel.org/r/20200616225409.4670-1-william.kucharski@xxxxxxxxxx Signed-off-by: William Kucharski <william.kucharski@xxxxxxxxxx> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slab_common.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) --- a/mm/slab_common.c~mm-ksize-should-silently-accept-a-null-pointer +++ a/mm/slab_common.c @@ -1681,10 +1681,9 @@ static __always_inline void *__do_kreall gfp_t flags) { void *ret; - size_t ks = 0; + size_t ks; - if (p) - ks = ksize(p); + ks = ksize(p); if (ks >= new_size) { p = kasan_krealloc((void *)p, new_size, flags); @@ -1744,10 +1743,9 @@ void kfree_sensitive(const void *p) size_t ks; void *mem = (void *)p; - if (unlikely(ZERO_OR_NULL_PTR(mem))) - return; ks = ksize(mem); - memzero_explicit(mem, ks); + if (ks) + memzero_explicit(mem, ks); kfree(mem); } EXPORT_SYMBOL(kfree_sensitive); @@ -1770,8 +1768,6 @@ size_t ksize(const void *objp) { size_t size; - if (WARN_ON_ONCE(!objp)) - return 0; /* * We need to check that the pointed to object is valid, and only then * unpoison the shadow memory below. We use __kasan_check_read(), to @@ -1785,7 +1781,7 @@ size_t ksize(const void *objp) * We want to perform the check before __ksize(), to avoid potentially * crashing in __ksize() due to accessing invalid metadata. */ - if (unlikely(objp == ZERO_SIZE_PTR) || !__kasan_check_read(objp, 1)) + if (unlikely(ZERO_OR_NULL_PTR(objp)) || !__kasan_check_read(objp, 1)) return 0; size = __ksize(objp); _
