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[34.78.62.124]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ee0fbc7188sm8551386f8f.37.2025.09.19.07.57.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Sep 2025 07:57:59 -0700 (PDT) From: Ethan Graham To: ethangraham@google.com, glider@google.com Cc: andreyknvl@gmail.com, andy@kernel.org, brauner@kernel.org, brendan.higgins@linux.dev, davem@davemloft.net, davidgow@google.com, dhowells@redhat.com, dvyukov@google.com, elver@google.com, herbert@gondor.apana.org.au, ignat@cloudflare.com, jack@suse.cz, jannh@google.com, johannes@sipsolutions.net, kasan-dev@googlegroups.com, kees@kernel.org, kunit-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lukas@wunner.de, rmoar@google.com, shuah@kernel.org, sj@kernel.org, tarasmadan@google.com Subject: [PATCH v2 01/10] mm/kasan: implement kasan_poison_range Date: Fri, 19 Sep 2025 14:57:41 +0000 Message-ID: <20250919145750.3448393-2-ethan.w.s.graham@gmail.com> X-Mailer: git-send-email 2.51.0.470.ga7dc726c21-goog In-Reply-To: <20250919145750.3448393-1-ethan.w.s.graham@gmail.com> References: <20250919145750.3448393-1-ethan.w.s.graham@gmail.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Alexander Potapenko --- PR v1: - Enforce KASAN_GRANULE_SIZE alignment for the end of the range in kasan_poison_range(), and return -EINVAL when this isn't respected. --- --- include/linux/kasan.h | 11 +++++++++++ mm/kasan/shadow.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 890011071f2b..cd6cdf732378 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -102,6 +102,16 @@ static inline bool kasan_has_integrated_init(void) } #ifdef CONFIG_KASAN + +/** + * kasan_poison_range - poison the memory range [@addr, @addr + @size) + * + * The exact behavior is subject to alignment with KASAN_GRANULE_SIZE, defined + * in : if @start is unaligned, the initial partial granule + * at the beginning of the range is only poisoned if CONFIG_KASAN_GENERIC=y. + */ +int kasan_poison_range(const void *addr, 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 +412,7 @@ static __always_inline bool kasan_check_byte(const void *addr) #else /* CONFIG_KASAN */ +static inline int kasan_poison_range(const void *start, size_t size) { return 0; } static inline void kasan_unpoison_range(const void *address, size_t size) {} static inline void kasan_poison_pages(struct page *page, unsigned int order, bool init) {} diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index d2c70cd2afb1..7faed02264f2 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -147,6 +147,40 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) } EXPORT_SYMBOL_GPL(kasan_poison); +int kasan_poison_range(const void *addr, size_t size) +{ + uintptr_t start_addr = (uintptr_t)addr; + uintptr_t head_granule_start; + uintptr_t poison_body_start; + uintptr_t poison_body_end; + size_t head_prefix_size; + uintptr_t end_addr; + + if ((start_addr + size) % KASAN_GRANULE_SIZE) + return -EINVAL; + + end_addr = ALIGN_DOWN(start_addr + size, KASAN_GRANULE_SIZE); + if (start_addr >= end_addr) + return -EINVAL; + + head_granule_start = ALIGN_DOWN(start_addr, KASAN_GRANULE_SIZE); + head_prefix_size = 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 = ALIGN(start_addr, KASAN_GRANULE_SIZE); + poison_body_end = 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); + return 0; +} +EXPORT_SYMBOL(kasan_poison_range); + #ifdef CONFIG_KASAN_GENERIC void kasan_poison_last_granule(const void *addr, size_t size) { -- 2.51.0.470.ga7dc726c21-goog