* [PATCH] fbdev: uvesafb: replace deprecated strncpy with strscpy_pad
@ 2024-03-20 23:04 Justin Stitt
2024-03-29 4:05 ` Kees Cook
0 siblings, 1 reply; 2+ messages in thread
From: Justin Stitt @ 2024-03-20 23:04 UTC (permalink / raw
To: Michal Januszewski, Helge Deller
Cc: linux-fbdev, dri-devel, linux-kernel, linux-hardening,
Justin Stitt
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 v86d_path to be NUL-terminated based on its use with the
C-string format specifier in printf-likes:
| pr_err("failed to execute %s\n", v86d_path);
and
| return snprintf(buf, PAGE_SIZE, "%s\n", v86d_path);
Let's also opt to pad v86d_path since it may get used in and around
userspace:
| return call_usermodehelper(v86d_path, argv, envp, UMH_WAIT_PROC);
Considering the above, strscpy_pad() is the best replacement as it
guarantees both NUL-termination and NUL-padding on the destination
buffer.
Note that this patch relies on the _new_ 2-argument versions of
strscpy() and strscpy_pad() introduced in Commit e6584c3964f2f ("string:
Allow 2-argument strscpy()").
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
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.
Found with: $ rg "strncpy\("
---
drivers/video/fbdev/uvesafb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/uvesafb.c b/drivers/video/fbdev/uvesafb.c
index e1f421e91b4f..8b554fcf1bfb 100644
--- a/drivers/video/fbdev/uvesafb.c
+++ b/drivers/video/fbdev/uvesafb.c
@@ -1867,7 +1867,7 @@ static ssize_t v86d_show(struct device_driver *dev, char *buf)
static ssize_t v86d_store(struct device_driver *dev, const char *buf,
size_t count)
{
- strncpy(v86d_path, buf, PATH_MAX - 1);
+ strscpy_pad(v86d_path, buf);
return count;
}
static DRIVER_ATTR_RW(v86d);
---
base-commit: a4145ce1e7bc247fd6f2846e8699473448717b37
change-id: 20240320-strncpy-drivers-video-fbdev-uvesafb-c-43668c4ef6c8
Best regards,
--
Justin Stitt <justinstitt@google.com>
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] fbdev: uvesafb: replace deprecated strncpy with strscpy_pad
2024-03-20 23:04 [PATCH] fbdev: uvesafb: replace deprecated strncpy with strscpy_pad Justin Stitt
@ 2024-03-29 4:05 ` Kees Cook
0 siblings, 0 replies; 2+ messages in thread
From: Kees Cook @ 2024-03-29 4:05 UTC (permalink / raw
To: Justin Stitt
Cc: Michal Januszewski, Helge Deller, linux-fbdev, dri-devel,
linux-kernel, linux-hardening
On Wed, Mar 20, 2024 at 11:04:44PM +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 v86d_path to be NUL-terminated based on its use with the
> C-string format specifier in printf-likes:
> | pr_err("failed to execute %s\n", v86d_path);
> and
> | return snprintf(buf, PAGE_SIZE, "%s\n", v86d_path);
>
> Let's also opt to pad v86d_path since it may get used in and around
> userspace:
> | return call_usermodehelper(v86d_path, argv, envp, UMH_WAIT_PROC);
>
> Considering the above, strscpy_pad() is the best replacement as it
> guarantees both NUL-termination and NUL-padding on the destination
> buffer.
>
> Note that this patch relies on the _new_ 2-argument versions of
> strscpy() and strscpy_pad() introduced in Commit e6584c3964f2f ("string:
> Allow 2-argument strscpy()").
>
> 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
> 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>
--
Kees Cook
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