linux-kernel - Re: [v2] wifi: atmel: replace deprecated strncpy with strscpy

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Message-ID: <169808225560.695306.1625165630823500076.kvalo@kernel.org>
Date:   Mon, 23 Oct 2023 17:30:57 +0000 (UTC)
From:   Kalle Valo <kvalo@...nel.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: Re: [v2] wifi: atmel: replace deprecated strncpy with strscpy

Justin Stitt <justinstitt@...gle.com> 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 priv->firmware_id to be NUL-terminated based on its usage
> with seq_printf() and strlen() in atmel.c:
> 1420 |       seq_printf(m, "%s loaded by host\n", priv->firmware_id);
> ...
> 3884 |       if (strlen(priv->firmware_id) == 0) {
> 
> NUL-padding is not required, which is evident by the usage of a plain
> strcpy():
> 3891 |   strcpy(priv->firmware_id, "atmel_at76c502.bin");
> 
> 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 replace hard-coded lengths to be `sizeof(...)` for buffers
> that the compiler can detect the size for as this is less error prone.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [2]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

Failed to apply:

Recorded preimage for 'drivers/net/wireless/atmel/atmel.c'
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Applying: wifi: atmel: replace deprecated strncpy with strscpy
Using index info to reconstruct a base tree...
M	drivers/net/wireless/atmel/atmel.c
Falling back to patching base and 3-way merge...
Auto-merging drivers/net/wireless/atmel/atmel.c
CONFLICT (content): Merge conflict in drivers/net/wireless/atmel/atmel.c
Patch failed at 0001 wifi: atmel: replace deprecated strncpy with strscpy

Patch set to Changes Requested.

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20231019-strncpy-drivers-net-wireless-atmel-atmel-c-v2-1-52e46fbea083@google.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches