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Date:   Wed, 27 Sep 2023 06:17:34 +0000
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Message-ID: <20230927-strncpy-drivers-misc-ti-st-st_kim-c-v1-1-29bbdeed1a2c@google.com>
Subject: [PATCH] drivers: misc: ti-st: replace deprecated strncpy with strscpy
From:   Justin Stitt <justinstitt@google.com>
To:     Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
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Precedence: bulk

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect both `kim_data->dev_name` and `kim_gdata->dev_name` to be
NUL-terminated.

`kim_data->dev_name` seems to not require NUL-padding.

`kim_gdata` is already zero-allocated and as such does not require
NUL-padding:
|       kim_gdata = kzalloc(sizeof(struct kim_data_s), GFP_KERNEL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.
---
 drivers/misc/ti-st/st_kim.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/ti-st/st_kim.c b/drivers/misc/ti-st/st_kim.c
index fe682e0553b2..a034b5d8b585 100644
--- a/drivers/misc/ti-st/st_kim.c
+++ b/drivers/misc/ti-st/st_kim.c
@@ -590,7 +590,7 @@ static ssize_t store_dev_name(struct device *dev,
 {
 	struct kim_data_s *kim_data = dev_get_drvdata(dev);
 	pr_debug("storing dev name >%s<", buf);
-	strncpy(kim_data->dev_name, buf, count);
+	strscpy(kim_data->dev_name, buf, count);
 	pr_debug("stored dev name >%s<", kim_data->dev_name);
 	return count;
 }
@@ -751,7 +751,8 @@ static int kim_probe(struct platform_device *pdev)
 	}
 
 	/* copying platform data */
-	strncpy(kim_gdata->dev_name, pdata->dev_name, UART_DEV_NAME_LEN);
+	strscpy(kim_gdata->dev_name, pdata->dev_name,
+		sizeof(kim_gdata->dev_name));
 	kim_gdata->flow_cntrl = pdata->flow_cntrl;
 	kim_gdata->baud_rate = pdata->baud_rate;
 	pr_info("sysfs entries created\n");

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230927-strncpy-drivers-misc-ti-st-st_kim-c-e1663a211a0c

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