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Wysocki" , Len Brown , linux-acpi@vger.kernel.org, "Gustavo A. R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 35/82] ACPI: custom_method: Refactor intentional wrap-around test Date: Mon, 22 Jan 2024 16:27:10 -0800 Message-Id: <20240123002814.1396804-35-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1829; i=keescook@chromium.org; h=from:subject; bh=EmH/DZbTBXxe0dWdplwnDgyJ2eUGGILv5amEUByys6s=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgHHHr/VKg/KAlcqjdcF5SYPKo1cfb9YxYbN Ub5YAXr20iJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8IBwAKCRCJcvTf3G3A Jm9OD/42OVFSF2SZuj2/Xm3blXVzWso1EIjDFteNwkRAzj/OhbsOveDY28YTwAprTxSc4mfzKh2 r7wc8fydFpA5Y8yVoR5Jq17o3YOw7xu8gZiX8GUHzRZRLiI88Bn0jOqyO96m5KRz/Oku4J9OJ1n lmgM7ubTGbc02BXB8oXJyNpBdVzqIOlNwD/ECpnxos42xDCcYITE6BC+/JUaUTVtU3usc2e03+B TwiHzcwD6iRnWxRxmVXnPXQPaaRaHWhyeGbhoWy30SFcvTY0EFAKqcwzZ/HggSCogQiktvuo4jw yKlwoj8AIcEquL/jcpRDgr1y8ZIO9gbut1BiyYhWI4QNFcP+uDl6R36CWESOrfqtgF2FhHrxI8w +YNsJz1cVkXUm4++MjtKT1gQym/CI6Yo6CEatJSvLwV7UE+LvUU9Q03t27lqUKhe9zCK5IRhOKm n5j9sTlJJJdJJTul3h3jXlEbP6Incxf0zT/TPVJuwAVlmJPtH1PyZ+c0TIzPgU4F+n6SL8Pho79 r8x2Q0FTlvu5RWYgG4P4HsGROu/rEfLajxdjnTbMLliKam77rFXZcJohT4UHLycRLcvT+2wuTrL 1Iesm634rNZPYYLnMax9FyEZwv0Q2Y1lQEFiSybEDKXGM4pheL3Dba5LCqYt2434cbDGUg0vfpk 77kzj9tRg0KuJ7Q== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: "Rafael J. Wysocki" Cc: Len Brown Cc: linux-acpi@vger.kernel.org Signed-off-by: Kees Cook --- drivers/acpi/custom_method.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index d39a9b474727..0789317f4a1a 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -54,7 +54,7 @@ static ssize_t cm_write(struct file *file, const char __user *user_buf, if ((*ppos > max_size) || (*ppos + count > max_size) || - (*ppos + count < count) || + (add_would_overflow(count, *ppos)) || (count > uncopied_bytes)) { kfree(buf); buf = NULL;