linux-hardening - [PATCH] dax: refactor deprecated strncpy

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Date:   Wed, 13 Sep 2023 01:10:24 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>
Cc:     nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] dax: refactor deprecated strncpy

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

We should prefer more robust and less ambiguous string interfaces.

`dax_id->dev_name` is expected to be NUL-terminated and has been zero-allocated.

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on the destination buffer. Moreover, due to
`dax_id` being zero-allocated the padding behavior of `strncpy` is not
needed and a simple 1:1 replacement of strncpy -> strscpy should
suffice.

Link: https://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/dax/bus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 0ee96e6fc426..1659b787b65f 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -103,7 +103,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
 		if (action == ID_ADD) {
 			dax_id = kzalloc(sizeof(*dax_id), GFP_KERNEL);
 			if (dax_id) {
-				strncpy(dax_id->dev_name, buf, DAX_NAME_LEN);
+				strscpy(dax_id->dev_name, buf, DAX_NAME_LEN);
 				list_add(&dax_id->list, &dax_drv->ids);
 			} else
 				rc = -ENOMEM;

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230913-strncpy-drivers-dax-bus-c-f12e3153e44b

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