From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
commit fdb54d96600aafe45951f549866cd6fc1af59954 upstream.
Commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated
kmalloc space than requested") added precise kmalloc redzone poisoning to
the slub_debug functionality.
However, this commit didn't account for HW_TAGS KASAN fully initializing
the object via its built-in memory initialization feature. Even though
HW_TAGS KASAN memory initialization contains special memory initialization
handling for when slub_debug is enabled, it does not account for in-object
slub_debug redzones. As a result, HW_TAGS KASAN can overwrite these
redzones and cause false-positive slub_debug reports.
To fix the issue, avoid HW_TAGS KASAN memory initialization when
slub_debug is enabled altogether. Implement this by moving the
__slub_debug_enabled check to slab_post_alloc_hook. Common slab code
seems like a more appropriate place for a slub_debug check anyway.
Link: https://lkml.kernel.org/r/678ac92ab790dba9198f9ca14f405651b97c8502.1688561016.git.andreyknvl@xxxxxxxxxx
Fixes: 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated kmalloc space than requested")
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reported-by: Will Deacon <will@xxxxxxxxxx>
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Feng Tang <feng.tang@xxxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: kasan-dev@xxxxxxxxxxxxxxxx
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/kasan/kasan.h | 12 ------------
mm/slab.h | 16 ++++++++++++++--
2 files changed, 14 insertions(+), 14 deletions(-)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -466,18 +466,6 @@ static inline void kasan_unpoison(const
if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
return;
- /*
- * Explicitly initialize the memory with the precise object size to
- * avoid overwriting the slab redzone. This disables initialization in
- * the arch code and may thus lead to performance penalty. This penalty
- * does not affect production builds, as slab redzones are not enabled
- * there.
- */
- if (__slub_debug_enabled() &&
- init && ((unsigned long)size & KASAN_GRANULE_MASK)) {
- init = false;
- memzero_explicit((void *)addr, size);
- }
size = round_up(size, KASAN_GRANULE_SIZE);
hw_set_mem_tag_range((void *)addr, size, tag, init);
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -684,6 +684,7 @@ static inline void slab_post_alloc_hook(
unsigned int orig_size)
{
unsigned int zero_size = s->object_size;
+ bool kasan_init = init;
size_t i;
flags &= gfp_allowed_mask;
@@ -701,6 +702,17 @@ static inline void slab_post_alloc_hook(
zero_size = orig_size;
/*
+ * When slub_debug is enabled, avoid memory initialization integrated
+ * into KASAN and instead zero out the memory via the memset below with
+ * the proper size. Otherwise, KASAN might overwrite SLUB redzones and
+ * cause false-positive reports. This does not lead to a performance
+ * penalty on production builds, as slub_debug is not intended to be
+ * enabled there.
+ */
+ if (__slub_debug_enabled())
+ kasan_init = false;
+
+ /*
* As memory initialization might be integrated into KASAN,
* kasan_slab_alloc and initialization memset must be
* kept together to avoid discrepancies in behavior.
@@ -708,8 +720,8 @@ static inline void slab_post_alloc_hook(
* As p[i] might get tagged, memset and kmemleak hook come after KASAN.
*/
for (i = 0; i < size; i++) {
- p[i] = kasan_slab_alloc(s, p[i], flags, init);
- if (p[i] && init && !kasan_has_integrated_init())
+ p[i] = kasan_slab_alloc(s, p[i], flags, kasan_init);
+ if (p[i] && init && (!kasan_init || !kasan_has_integrated_init()))
memset(p[i], 0, zero_size);
kmemleak_alloc_recursive(p[i], s->object_size, 1,
s->flags, flags);
