linux-hardening - Re: [PATCH] SUNRPC: Replace strlcpy with strscpy

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Date:   Tue, 13 Jun 2023 14:18:06 +0000
From:   Chuck Lever III <chuck.lever@...cle.com>
To:     Azeem Shaikh <azeemshaikh38@...il.com>
CC:     Jeff Layton <jlayton@...nel.org>,
        "linux-hardening@...r.kernel.org" <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 Mailing List <linux-nfs@...r.kernel.org>,
        open list <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" <netdev@...r.kernel.org>
Subject: Re: [PATCH] SUNRPC: Replace strlcpy with strscpy



> On Jun 12, 2023, at 8:40 PM, 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 strscpy().

Using sprintf() seems cleaner to me: it would get rid of
the undocumented naked integer. Would that work for you?


> Direct replacement is safe here since the getter in kernel_params_ops
> handles -errorno return [3].

s/errorno/errno/


> [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..e5f379c4fdb3 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 strscpy(buf, "auto\n", 20);
> case SVC_POOL_GLOBAL:
> - return strlcpy(buf, "global\n", 20);
> + return strscpy(buf, "global\n", 20);
> case SVC_POOL_PERCPU:
> - return strlcpy(buf, "percpu\n", 20);
> + return strscpy(buf, "percpu\n", 20);
> case SVC_POOL_PERNODE:
> - return strlcpy(buf, "pernode\n", 20);
> + return strscpy(buf, "pernode\n", 20);
> default:
> return sprintf(buf, "%d\n", *ip);
> }
> -- 
> 2.41.0.162.gfafddb0af9-goog
> 
> 

--
Chuck Lever