drivers: misc: ti-st: replace deprecated strncpy with strscpy

`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.

Let's also opt to use the more idiomatic strscpy usage of:
strscpy(dest, src, sizeof(dest))

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231003-strncpy-drivers-misc-ti-st-st_kim-c-v2-1-79630447b0a1@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/ti-st/st_kim.c b/drivers/misc/ti-st/st_kim.c
index fe682e0553b2c139b0df6f991e783f1d9d1e47c4..4b1be0bb6ac099fdfadb7e136440655693ba4fab 100644 (file)
--- 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, sizeof(kim_data->dev_name));
        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");