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Mon, 17 Aug 2026 11:33:02 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav02.fra02v.mail.ibm.com (Postfix) with SMTP; Mon, 17 Aug 2026 11:33:02 +0000 (GMT) Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 55669) id 4520F16158E; Mon, 17 Aug 2026 13:33:02 +0200 (CEST) From: Alexander Gordeev To: Gerald Schaefer , Heiko Carstens , Christian Borntraeger , Vasily Gorbik , Claudio Imbrenda , Andrey Ryabinin Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com Subject: [PATCH v7 3/4] mm/kasan: Introduce helpers for lazy MMU mode sanitizer Date: Mon, 17 Aug 2026 13:33:01 +0200 Message-ID: <52c9be0cf71a8896a5d76c148c38fb24a2005dd9.1786956464.git.agordeev@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=OfaoyBTY c=1 sm=1 tr=0 ts=6a82f173 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=IbWDVZlrxelGz4sJbtUA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwODE3MDA4NyBTYWx0ZWRfX/+4fCm+gB8G5 2RiCBOZ5NlJZvsXwGYWFydnkDo34qYfthGKQCJbUOyHaple9d98NY3YLKRwJcf8gpEWbHvnrMeH 6JGJFsmPNeRAJne6CexoFGMml+6ch3M= X-Proofpoint-GUID: MvG7Ke4FAqGi8_-4CsoJlgvNnyj77p6- X-Proofpoint-ORIG-GUID: 4FUd8_M_4TIG6n8IU5tDLQ4GcyZLYqRk X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE3MDA4NyBTYWx0ZWRfX2eQZRCnxwWvx fnOALfM7tJTiqmdqDCg2Sh3ONESzXkCr+X1GA28FyKgpDC5mykDFi9/t/tWux/SVU0/VKfTKo/4 hQe/fvG15tB0Y93meOzvepWHC7N4N/Pn6taHrReNlTpwQs0t414PSXNzlxqLFRr4OnLUHv6BNHd RBnp5EvYzvRa9EnXIBDTnBo6waavwhrorFitsQbqvyCQyJO3xAryNiRmn/7vw13gY4PhrX2D14Q 48ACbzqux7ufXqtCg/MvzYSidJSpy/k8w2Ah9AuEW0tgKVVi0v573LgwY1FclMVYUsLKbp7XKoI Iptwv1An+252M8/k05KhTS3/57P6hkuM+qM7A6uaXLxiL5XRFwGO7z0mfk8HvCqL5IaE0IDbeDe u6bd6Z6VFaDVFKAkJkh1KCfhtl6lN+BvUQriRuelMo+le0w2E4nW6+YnDk+Zud0BG+8pWxDHJgu nvqBVX+EBEq+16SJyxA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-16_06,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 malwarescore=0 bulkscore=0 phishscore=0 priorityscore=1501 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608170087 Provide helpers that allow architectures implement illegitimate PTE direct accesses while the lazy MMU mode is enabled, such as: pte_t pte =3D *ptep; *ptep =3D pte; By contrast, these would have to be: pte_t pte =3D ptep_get(ptep); set_pte(ptep, pte); The direct PTE accesses pose a real issue on s390. Suggested-by: Ilya Leoshkevich Signed-off-by: Alexander Gordeev --- include/linux/kasan.h | 19 +++++++++++++++++-- mm/kasan/common.c | 14 ++++++++++++++ mm/kasan/kasan.h | 2 ++ mm/kasan/report_generic.c | 3 +++ 4 files changed, 36 insertions(+), 2 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index bf233bde68c7..1aa4d9dd2485 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -6,6 +6,7 @@ #include #include #include +#include #include #include =20 @@ -35,8 +36,6 @@ typedef unsigned int __bitwise kasan_vmalloc_flags_t; =20 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) =20 -#include - /* Software KASAN implementations use shadow memory. */ =20 #ifdef CONFIG_KASAN_SW_TAGS @@ -134,6 +133,20 @@ static __always_inline void kasan_poison_slab(struct= slab *slab) __kasan_poison_slab(slab); } =20 +void __kasan_poison_pte(pte_t *pte, int nr); +static __always_inline void kasan_poison_pte(pte_t *pte, int nr) +{ + if (kasan_enabled()) + __kasan_poison_pte(pte, nr); +} + +void __kasan_unpoison_pte(pte_t *pte, int nr); +static __always_inline void kasan_unpoison_pte(pte_t *pte, int nr) +{ + if (kasan_enabled()) + __kasan_unpoison_pte(pte, nr); +} + void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object)= ; /** * kasan_unpoison_new_object - Temporarily unpoison a new slab object. @@ -414,6 +427,8 @@ static inline bool kasan_unpoison_pages(struct page *= page, unsigned int order, return false; } static inline void kasan_poison_slab(struct slab *slab) {} +static inline void kasan_poison_pte(pte_t *pte, int nr) {} +static inline void kasan_unpoison_pte(pte_t *pte, int nr) {} static inline void kasan_unpoison_new_object(struct kmem_cache *cache, void *object) {} static inline void kasan_poison_new_object(struct kmem_cache *cache, diff --git a/mm/kasan/common.c b/mm/kasan/common.c index b7d05c2a6d93..94d106094989 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -163,6 +163,20 @@ void __kasan_poison_slab(struct slab *slab) KASAN_SLAB_REDZONE, false); } =20 +void __kasan_poison_pte(pte_t *pte, int nr) +{ + if (IS_ALIGNED(sizeof(*pte), KASAN_GRANULE_SIZE)) + kasan_poison(pte, sizeof(*pte) * nr, KASAN_LAZY_MMU_PTE, false); +} +EXPORT_SYMBOL_GPL(__kasan_poison_pte); + +void __kasan_unpoison_pte(pte_t *pte, int nr) +{ + if (IS_ALIGNED(sizeof(*pte), KASAN_GRANULE_SIZE)) + kasan_unpoison(pte, sizeof(*pte) * nr, false); +} +EXPORT_SYMBOL_GPL(__kasan_unpoison_pte); + void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object) { kasan_unpoison(object, cache->object_size, false); diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index fc9169a54766..1a2d18cdb21d 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -144,12 +144,14 @@ static inline bool kasan_requires_meta(void) #define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocation= */ #define KASAN_SLAB_REDZONE 0xFC /* redzone for slab object */ #define KASAN_SLAB_FREE 0xFB /* freed slab object */ +#define KASAN_LAZY_MMU_PTE 0xFD /* direct pte access in lazy mmu mode *= / #define KASAN_VMALLOC_INVALID 0xF8 /* inaccessible space in vmap area *= / #else #define KASAN_PAGE_FREE KASAN_TAG_INVALID #define KASAN_PAGE_REDZONE KASAN_TAG_INVALID #define KASAN_SLAB_REDZONE KASAN_TAG_INVALID #define KASAN_SLAB_FREE KASAN_TAG_INVALID +#define KASAN_LAZY_MMU_PTE KASAN_TAG_INVALID #define KASAN_VMALLOC_INVALID KASAN_TAG_INVALID /* only used for SW_TAGS= */ #endif =20 diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c index f5b8e37b3805..489d4a8d6902 100644 --- a/mm/kasan/report_generic.c +++ b/mm/kasan/report_generic.c @@ -113,6 +113,9 @@ static const char *get_shadow_bug_type(struct kasan_r= eport_info *info) case KASAN_SLAB_FREE_META: bug_type =3D "slab-use-after-free"; break; + case KASAN_LAZY_MMU_PTE: + bug_type =3D "lazy-mmu-pte-access"; + break; case KASAN_ALLOCA_LEFT: case KASAN_ALLOCA_RIGHT: bug_type =3D "alloca-out-of-bounds"; --=20 2.53.0