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Date:   Tue, 13 Jun 2023 18:04:19 -0700
From:   Kees Cook <kees@kernel.org>
To:     Azeem Shaikh <azeemshaikh38@gmail.com>,
        Chuck Lever <chuck.lever@oracle.com>,
        Jeff Layton <jlayton@kernel.org>,
        Kees Cook <keescook@chromium.org>
CC:     linux-hardening@vger.kernel.org, Neil Brown <neilb@suse.de>,
        Olga Kornievskaia <kolga@netapp.com>,
        Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
        linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org
Subject: Re: [PATCH v2] SUNRPC: Remove strlcpy
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On June 13, 2023 5:12:46 PM PDT, Azeem Shaikh <azeemshaikh38@gmail=2Ecom> w=
rote:
>strlcpy() reads the entire source buffer first=2E
>This read may exceed the destination size limit=2E
>This is both inefficient and can lead to linear read
>overflows if a source string is not NUL-terminated [1]=2E
>In an effort to remove strlcpy() completely [2], replace
>strlcpy() here with sysfs_emit()=2E
>
>Direct replacement is safe here since the getter in kernel_params_ops
>handles -errno return [3]=2E
>
>[1] https://www=2Ekernel=2Eorg/doc/html/latest/process/deprecated=2Ehtml#=
strlcpy
>[2] https://github=2Ecom/KSPP/linux/issues/89
>[3] https://elixir=2Ebootlin=2Ecom/linux/v6=2E4-rc6/source/include/linux/=
moduleparam=2Eh#L52
>
>Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail=2Ecom>
>---
> net/sunrpc/svc=2Ec |    8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/net/sunrpc/svc=2Ec b/net/sunrpc/svc=2Ec
>index e6d4cec61e47=2E=2E77326f163801 100644
>--- a/net/sunrpc/svc=2Ec
>+++ b/net/sunrpc/svc=2Ec
>@@ -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_e=
mit" or so)=2E

-Kees


--=20
Kees Cook