linux-kernel - Re: [PATCH v2] SUNRPC: Remove strlcpy

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Message-ID: <CADmuW3VcK4zH0oOi8JxsdNvVwfxz+hf-aabLtf4xOJuYtM+jzA@mail.gmail.com>
Date:   Tue, 13 Jun 2023 21:10:53 -0400
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Kees Cook <kees@...nel.org>
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Kees Cook <keescook@...omium.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@...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 Tue, Jun 13, 2023 at 9:04 PM Kees Cook <kees@...nel.org> wrote:
>
> 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).

Ah sorry, I missed the "replace default sprintf too" part in the
previous thread. Resending.

>
> -Kees
>
>
>
> --
> Kees Cook