linux-hardening - [PATCH] accel/ivpu: refactor deprecated strncpy

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Date:   Thu, 24 Aug 2023 21:20:25 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
        Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>,
        Oded Gabbay <ogabbay@...nel.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] accel/ivpu: refactor deprecated strncpy

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on its destination buffer argument which is
_not_ the case for `strncpy`!

Also remove extraneous if-statement as it can never be entered. The
return value from `strncpy` is it's first argument. In this case,
`...dyndbg_cmd` is an array:
| 	char dyndbg_cmd[VPU_DYNDBG_CMD_MAX_LEN];
             ^^^^^^^^^^
This can never be NULL which means `strncpy`'s return value cannot be
NULL here. Just use `strscpy` which is more robust and results in
simpler and less ambiguous code.

Moreover, remove needless `... - 1` as `strscpy`'s implementation
ensures NUL-termination and we do not need to carefully dance around
ending boundaries with a "- 1" anymore.

Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.
---
 drivers/accel/ivpu/ivpu_jsm_msg.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/accel/ivpu/ivpu_jsm_msg.c b/drivers/accel/ivpu/ivpu_jsm_msg.c
index 831bfd2b2d39..bdddef2c59ee 100644
--- a/drivers/accel/ivpu/ivpu_jsm_msg.c
+++ b/drivers/accel/ivpu/ivpu_jsm_msg.c
@@ -118,8 +118,7 @@ int ivpu_jsm_dyndbg_control(struct ivpu_device *vdev, char *command, size_t size
 	struct vpu_jsm_msg resp;
 	int ret;
 
-	if (!strncpy(req.payload.dyndbg_control.dyndbg_cmd, command, VPU_DYNDBG_CMD_MAX_LEN - 1))
-		return -ENOMEM;
+	strscpy(req.payload.dyndbg_control.dyndbg_cmd, command, VPU_DYNDBG_CMD_MAX_LEN);
 
 	ret = ivpu_ipc_send_receive(vdev, &req, VPU_JSM_MSG_DYNDBG_CONTROL_RSP, &resp,
 				    VPU_IPC_CHAN_ASYNC_CMD, vdev->timeout.jsm);

---
base-commit: f9604036a3fb6149badf346994b46b03f9292db7
change-id: 20230824-strncpy-drivers-accel-ivpu-ivpu_jsm_msg-c-2422f7f00fc8

Best regards,
--
Justin Stitt <justinstitt@...gle.com>