linux-hardening - Re: [PATCH v4] arm64/sysreg: refactor deprecated strncpy

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Date:   Wed, 6 Sep 2023 19:48:50 +0100
From:   Will Deacon <will@...nel.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Mostafa Saleh <smostafa@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4] arm64/sysreg: refactor deprecated strncpy

On Tue, Sep 05, 2023 at 08:10:21PM +0000, Justin Stitt wrote:
> strncpy is deprecated [1] and should not be used if the src string is
> not NUL-terminated.
> 
> When dealing with `cmdline` we are counting the number of characters
> until a space then copying these over into `buf`. Let's not use any of
> the str*() functions since the src string is not necessarily NUL-terminated.
> 
> Prefer `memcpy()` alongside a forced NUL-termination as it more
> accurately describes what is going on within this function, i.e: copying
> from non NUL-terminated buffer into a NUL-terminated buffer.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Suggested-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Changes in v4:
> - rebase onto mainline (thanks Will)
> - Link to v3: https://lore.kernel.org/r/20230831-strncpy-arch-arm64-v3-1-cdbb1e7ea5e1@google.com

The original patch converting the strncpy() to strscpy() has already landed
upstream, so this doesn't apply as-is.

Rather than go through a v5, I've reverted your original patch and squashed
this on top with a new commit message. I'll push it out tomorrow on to the
arm64 fixes branch.

Thanks,

Will