Re: [PATCH v6] checkpatch: add check for snprintf to scnprintf

Lee Jones
2024-05-02T09:30:24Z

On Mon, 29 Apr 2024, Justin Stitt wrote:

> I am going to quote Lee Jones who has been doing some snprintf ->
> scnprintf refactorings:
>
> "There is a general misunderstanding amongst engineers that
> {v}snprintf() returns the length of the data *actually* encoded into the
> destination array. However, as per the C99 standard {v}snprintf()
> really returns the length of the data that *would have been* written if
> there were enough space for it. This misunderstanding has led to
> buffer-overruns in the past. It's generally considered safer to use the
> {v}scnprintf() variants in their place (or even sprintf() in simple
> cases). So let's do that."
>
> To help prevent new instances of snprintf() from popping up, let's add a
> check to checkpatch.pl.
>
> Suggested-by: Finn Thain <fthain@linux-m68k.org>
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Changes in v6:
> - move capture group to only include symbol name (not spaces or paren)
> - Link to v5: https://lore.kernel.org/r/20240422-snprintf-checkpatch-v5-1-f1e90bf7164e@google.com
>
> Changes in v5:
> - use capture groups to let the user know which variation they used
> - Link to v4: https://lore.kernel.org/r/20240408-snprintf-checkpatch-v4-1-8697c96ac94b@google.com
>
> Changes in v4:
> - also check for vsnprintf variant (thanks Bill)
> - Link to v3: https://lore.kernel.org/r/20240315-snprintf-checkpatch-v3-1-a451e7664306@google.com
>
> Changes in v3:
> - fix indentation
> - add reference link (https://github.com/KSPP/linux/issues/105) (thanks Joe)
> - Link to v2: https://lore.kernel.org/r/20240221-snprintf-checkpatch-v2-1-9baeb59dae30@google.com
>
> Changes in v2:
> - Had a vim moment and deleted a character before sending the patch.
> - Replaced the character :)
> - Link to v1: https://lore.kernel.org/r/20240221-snprintf-checkpatch-v1-1-3ac5025b5961@google.com
> ---
> From a discussion here [1].
>
> [1]: https://lore.kernel.org/all/0f9c95f9-2c14-eee6-7faf-635880edcea4@linux-m68k.org/
> ---
> scripts/checkpatch.pl | 6 ++++++
> 1 file changed, 6 insertions(+)

Reviewed-by: Lee Jones <lee@kernel.org>

--
Lee Jones [李琼斯]