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[34.76.220.87]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b8f8b1bc81sm25677444f8f.69.2025.08.13.06.38.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Aug 2025 06:38:39 -0700 (PDT) From: Ethan Graham To: ethangraham@google.com, glider@google.com Cc: andreyknvl@gmail.com, brendan.higgins@linux.dev, davidgow@google.com, dvyukov@google.com, jannh@google.com, elver@google.com, rmoar@google.com, shuah@kernel.org, tarasmadan@google.com, kasan-dev@googlegroups.com, kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v1 RFC 1/6] mm/kasan: implement kasan_poison_range Date: Wed, 13 Aug 2025 13:38:07 +0000 Message-ID: <20250813133812.926145-2-ethan.w.s.graham@gmail.com> X-Mailer: git-send-email 2.51.0.rc0.205.g4a044479a3-goog In-Reply-To: <20250813133812.926145-1-ethan.w.s.graham@gmail.com> References: <20250813133812.926145-1-ethan.w.s.graham@gmail.com> 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 Content-Type: text/plain; charset="utf-8" From: Ethan Graham Introduce a new helper function, kasan_poison_range(), to encapsulate the logic for poisoning an arbitrary memory range of a given size, and expose it publically in . This is a preparatory change for the upcoming KFuzzTest patches, which requires the ability to poison the inter-region padding in its input buffers. No functional change to any other subsystem is intended by this commit. Signed-off-by: Ethan Graham --- include/linux/kasan.h | 16 ++++++++++++++++ mm/kasan/shadow.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 890011071f2b..09baeb6c9f4d 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -102,6 +102,21 @@ static inline bool kasan_has_integrated_init(void) } =20 #ifdef CONFIG_KASAN + +/** + * kasan_poison_range - poison the memory range [start, start + size) + * + * The exact behavior is subject to alignment with KASAN_GRANULE_SIZE, def= ined + * in . + * + * - If @start is unaligned, the initial partial granule at the beginning + * of the range is only poisoned if CONFIG_KASAN_GENERIC is enabled. + * - The poisoning of the range only extends up to the last full granule b= efore + * the end of the range. Any remaining bytes in a final partial granule are + * ignored. + */ +void kasan_poison_range(const void *start, size_t size); + void __kasan_unpoison_range(const void *addr, size_t size); static __always_inline void kasan_unpoison_range(const void *addr, size_t = size) { @@ -402,6 +417,7 @@ static __always_inline bool kasan_check_byte(const void= *addr) =20 #else /* CONFIG_KASAN */ =20 +static inline void kasan_poison_range(const void *start, size_t size) {} static inline void kasan_unpoison_range(const void *address, size_t size) = {} static inline void kasan_poison_pages(struct page *page, unsigned int orde= r, bool init) {} diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index d2c70cd2afb1..a1b6bfb35f07 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -147,6 +147,37 @@ void kasan_poison(const void *addr, size_t size, u8 va= lue, bool init) } EXPORT_SYMBOL_GPL(kasan_poison); =20 +void kasan_poison_range(const void *start, size_t size) +{ + void *end =3D (char *)start + size; + uintptr_t start_addr =3D (uintptr_t)start; + uintptr_t head_granule_start; + uintptr_t poison_body_start; + uintptr_t poison_body_end; + size_t head_prefix_size; + uintptr_t end_addr; + + end_addr =3D ALIGN_DOWN((uintptr_t)end, KASAN_GRANULE_SIZE); + if (start_addr >=3D end_addr) + return; + + head_granule_start =3D ALIGN_DOWN(start_addr, KASAN_GRANULE_SIZE); + head_prefix_size =3D start_addr - head_granule_start; + + if (IS_ENABLED(CONFIG_KASAN_GENERIC) && head_prefix_size > 0) + kasan_poison_last_granule((void *)head_granule_start, + head_prefix_size); + + poison_body_start =3D ALIGN(start_addr, KASAN_GRANULE_SIZE); + poison_body_end =3D ALIGN_DOWN(end_addr, KASAN_GRANULE_SIZE); + + if (poison_body_start < poison_body_end) + kasan_poison((void *)poison_body_start, + poison_body_end - poison_body_start, + KASAN_SLAB_REDZONE, false); +} +EXPORT_SYMBOL(kasan_poison_range); + #ifdef CONFIG_KASAN_GENERIC void kasan_poison_last_granule(const void *addr, size_t size) { --=20 2.51.0.rc0.205.g4a044479a3-goog