On Wed, Sep 27, 2023 at 06:17:34AM +0000, Justin Stitt wrote:
> `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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> 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);
This is again the early truncation issue. This should use
sizeof(kim_data->dev_name). "buf" will be %NUL terminated already.
> 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));
This looks correct.
> 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 <[email protected]>
>
--
Kees Cook
