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AJvYcCUcipqMxi75Ap6THU4S8vYvzZz545QT1DZ0m6ITjA/b4j3Z3zwvGXem/tp8YWqj6J2qDWI42aBnDPTWJBAsEfU=@vger.kernel.org X-Gm-Message-State: AOJu0YyfDS3GSLXS+8k/FEzOUAKXB7KbGnwl964Rjg30LeNcDnUOzlrq gE/lqsbL4yjRg2VgVwH+jtjCz4znAcQu5R8M5ocwbn2SoqryWYNOxINcIUb7E21g9Q== X-Google-Smtp-Source: AGHT+IHw/mFa4K32w6FBmgVCLK0lfqwfx84tHmcbhBFHdeJjTz1GHC7yDdmMbL5MTLDA5q8NZ++fySA= X-Received: from pgcu63.prod.google.com ([2002:a63:7942:0:b0:af2:3541:76e2]) (user=pcc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:113:b0:1f5:874c:c987 with SMTP id adf61e73a8af0-1fe42f2c872mr24619131637.15.1742867785611; Mon, 24 Mar 2025 18:56:25 -0700 (PDT) Date: Mon, 24 Mar 2025 18:56:15 -0700 In-Reply-To: <20250325015617.23455-1-pcc@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250325015617.23455-1-pcc@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250325015617.23455-3-pcc@google.com> Subject: [PATCH v3 2/2] kasan: Add strscpy() test to trigger tag fault on arm64 From: Peter Collingbourne To: Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Kees Cook , Andy Shevchenko , Andrey Konovalov , Catalin Marinas , Mark Rutland Cc: Vincenzo Frascino , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Will Deacon , Peter Collingbourne From: Vincenzo Frascino When we invoke strscpy() with a maximum size of N bytes, it assumes that: - It can always read N bytes from the source. - It always write N bytes (zero-padded) to the destination. On aarch64 with Memory Tagging Extension enabled if we pass an N that is bigger then the source buffer, it triggers an MTE fault. Implement a KASAN KUnit test that triggers the issue with the current implementation of read_word_at_a_time() on aarch64 with MTE enabled. Cc: Will Deacon Signed-off-by: Vincenzo Frascino Signed-off-by: Catalin Marinas Co-developed-by: Peter Collingbourne Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/If88e396b9e7c058c1a4b5a252274120e77b1898a Reviewed-by: Andrey Konovalov --- v3: - simplify test case v2: - rebased - fixed test failure mm/kasan/kasan_test_c.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c index 59d673400085f..b69f66b7eda1d 100644 --- a/mm/kasan/kasan_test_c.c +++ b/mm/kasan/kasan_test_c.c @@ -1570,6 +1570,7 @@ static void kasan_memcmp(struct kunit *test) static void kasan_strings(struct kunit *test) { char *ptr; + char *src; size_t size = 24; /* @@ -1581,6 +1582,18 @@ static void kasan_strings(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + src = kmalloc(KASAN_GRANULE_SIZE, GFP_KERNEL | __GFP_ZERO); + strscpy(src, "f0cacc1a0000000", KASAN_GRANULE_SIZE); + + /* + * The expected size does not include the terminator '\0' + * so it is (KASAN_GRANULE_SIZE - 2) == + * KASAN_GRANULE_SIZE - ("initial removed character" + "\0"). + */ + KUNIT_EXPECT_EQ(test, KASAN_GRANULE_SIZE - 2, + strscpy(ptr, src + 1, KASAN_GRANULE_SIZE)); + + kfree(src); kfree(ptr); /*