netdev - Re: [PATCH v2] SUNRPC: Remove strlcpy

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Date: Tue, 13 Jun 2023 18:04:19 -0700
From: Kees Cook <kees@...nel.org>
To: Azeem Shaikh <azeemshaikh38@...il.com>, Chuck Lever <chuck.lever@...cle.com>,
 Jeff Layton <jlayton@...nel.org>, Kees Cook <keescook@...omium.org>
CC: linux-hardening@...r.kernel.org, Neil Brown <neilb@...e.de>,
 Olga Kornievskaia <kolga@...app.com>, Dai Ngo <Dai.Ngo@...cle.com>,
 Tom Talpey <tom@...pey.com>, linux-nfs@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Trond Myklebust <trond.myklebust@...merspace.com>,
 Anna Schumaker <anna@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] SUNRPC: Remove strlcpy

On June 13, 2023 5:12:46 PM PDT, Azeem Shaikh <azeemshaikh38@...il.com> wrote:
>strlcpy() reads the entire source buffer first.
>This read may exceed the destination size limit.
>This is both inefficient and can lead to linear read
>overflows if a source string is not NUL-terminated [1].
>In an effort to remove strlcpy() completely [2], replace
>strlcpy() here with sysfs_emit().
>
>Direct replacement is safe here since the getter in kernel_params_ops
>handles -errno return [3].
>
>[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
>[2] https://github.com/KSPP/linux/issues/89
>[3] https://elixir.bootlin.com/linux/v6.4-rc6/source/include/linux/moduleparam.h#L52
>
>Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
>---
> net/sunrpc/svc.c |    8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
>index e6d4cec61e47..77326f163801 100644
>--- a/net/sunrpc/svc.c
>+++ b/net/sunrpc/svc.c
>@@ -109,13 +109,13 @@ param_get_pool_mode(char *buf, const struct kernel_param *kp)
> 	switch (*ip)
> 	{
> 	case SVC_POOL_AUTO:
>-		return strlcpy(buf, "auto\n", 20);
>+		return sysfs_emit(buf, "auto\n");
> 	case SVC_POOL_GLOBAL:
>-		return strlcpy(buf, "global\n", 20);
>+		return sysfs_emit(buf, "global\n");
> 	case SVC_POOL_PERCPU:
>-		return strlcpy(buf, "percpu\n", 20);
>+		return sysfs_emit(buf, "percpu\n");
> 	case SVC_POOL_PERNODE:
>-		return strlcpy(buf, "pernode\n", 20);
>+		return sysfs_emit(buf, "pernode\n");
> 	default:
> 		return sprintf(buf, "%d\n", *ip);

Please replace the sprintf too (and then the Subject could be "use sysfs_emit" or so).

-Kees

-- 
Kees Cook