2023-09-18 10:12:23

by Justin Stitt

Subject: [PATCH v2] accessibility: speakup: refactor deprecated strncpy

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

Let's refactor this function to just use synth_write().

Link: http://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]>
Suggested-by: Kees Cook <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Tested-by: Samuel Thibault <[email protected]>
---
Changes from v1 -> v2:
- refactor synth_direct_store (thanks Kees)
- rebase onto 3669558bdf354cd352be955ef2764cde6a9bf5ec
- Link to v1: https://lore.kernel.org/all/20230824-strncpy-drivers-accessibility-speakup-kobjects-c-v1-1-3a1ef1221e90@google.com/
---
drivers/accessibility/speakup/kobjects.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/accessibility/speakup/kobjects.c b/drivers/accessibility/speakup/kobjects.c
index a7522d409802..0dfdb6608e02 100644
--- a/drivers/accessibility/speakup/kobjects.c
+++ b/drivers/accessibility/speakup/kobjects.c
@@ -413,27 +413,24 @@ static ssize_t synth_direct_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
- u_char tmp[256];
- int len;
- int bytes;
- const char *ptr = buf;
+ char *unescaped;
unsigned long flags;

if (!synth)
return -EPERM;

- len = strlen(buf);
+ unescaped = kstrdup(buf, GFP_KERNEL);
+ if (!unescaped)
+ return -ENOMEM;
+
+ string_unescape_any_inplace(unescaped);
+
spin_lock_irqsave(&speakup_info.spinlock, flags);
- while (len > 0) {
- bytes = min_t(size_t, len, 250);
- strncpy(tmp, ptr, bytes);
- tmp[bytes] = '\0';
- string_unescape_any_inplace(tmp);
- synth_printf("%s", tmp);
- ptr += bytes;
- len -= bytes;
- }
+ synth_write(unescaped, strlen(unescaped));
spin_unlock_irqrestore(&speakup_info.spinlock, flags);
+
+ kfree(unescaped);
+
return count;
}


---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230824-strncpy-drivers-accessibility-speakup-kobjects-c-4009e7df0936

Best regards,
--
Justin Stitt <[email protected]>

2023-10-03 23:56:36

by Kees Cook

Subject: Re: [PATCH v2] accessibility: speakup: refactor deprecated strncpy

On Mon, 18 Sep 2023 05:30:15 +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>
> Let's refactor this function to just use synth_write().
>
>

Thanks for the testing! It's been 2 week without any more comments,
so I'll snag this.

Applied to for-next/hardening, thanks!

[1/1] accessibility: speakup: refactor deprecated strncpy
https://git.kernel.org/kees/c/692c013e8f37

Take care,

--
Kees Cook