linux-kernel - Re: [PATCH v2 1/6] uaccess: Add copy_from_user

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Message-ID: <aWS9nOj4MAa7pYmS@google.com>
Date: Mon, 12 Jan 2026 09:23:40 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Fushuai Wang <fushuai.wang@...ux.dev>
Cc: tglx@...nel.org, peterz@...radead.org, mathieu.desnoyers@...icios.com, 
	akpm@...ux-foundation.org, yury.norov@...il.com, vmalik@...hat.com, 
	kees@...nel.org, dave.hansen@...ux.intel.com, luto@...nel.org, 
	mingo@...hat.com, bp@...en8.de, hpa@...or.com, rostedt@...dmis.org, 
	mhiramat@...nel.org, brauner@...nel.org, jack@...e.cz, cyphar@...har.com, 
	linux-kernel@...r.kernel.org, x86@...nel.org, 
	linux-trace-kernel@...r.kernel.org, wangfushuai@...du.com
Subject: Re: [PATCH v2 1/6] uaccess: Add copy_from_user_nul helper

On Mon, Jan 12, 2026 at 03:30:34PM +0800, Fushuai Wang wrote:
> From: Fushuai Wang <wangfushuai@...du.com>
> 
> Many places call copy_from_user() to copy a buffer from user space,
> and then manually add a NULL terminator to the destination buffer,
> e.g.:
> 
> 	if (copy_from_user(dest, src, len))
> 		return -EFAULT;
> 	dest[len] = '\0';
> 
> This is repetitive and error-prone. Add a copy_from_user_nul() helper to
> simplify such patterns. It copied n bytes from user space to kernel space,
> and NUL-terminates the destination buffer.
> 
> Signed-off-by: Fushuai Wang <wangfushuai@...du.com>

Hmm, this function is very very similar to strncpy_from_user(). Should
they be using that instead?

Alice