From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5126BC7EE23 for ; Sat, 13 May 2023 23:46:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229603AbjEMXqQ (ORCPT ); Sat, 13 May 2023 19:46:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229447AbjEMXqP (ORCPT ); Sat, 13 May 2023 19:46:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8780D1FD4; Sat, 13 May 2023 16:46:13 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1930560EEA; Sat, 13 May 2023 23:46:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3F43C433D2; Sat, 13 May 2023 23:46:11 +0000 (UTC) Date: Sat, 13 May 2023 19:46:09 -0400 From: Steven Rostedt To: Kees Cook Cc: Chuck Lever III , Azeem Shaikh , Jeff Layton , "linux-hardening@vger.kernel.org" , Linux NFS Mailing List , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] NFSD: Replace all non-returning strlcpy with strscpy Message-ID: <20230513194609.1b3121f6@rorschach.local.home> In-Reply-To: <202305110927.12508719D2@keescook> References: <20230510220952.3507366-1-azeemshaikh38@gmail.com> <72239648-C807-4CDD-8DA7-18440C83384E@oracle.com> <202305110927.12508719D2@keescook> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, 11 May 2023 09:32:31 -0700 Kees Cook wrote: > On Thu, May 11, 2023 at 02:47:54PM +0000, Chuck Lever III wrote: > > Hello Azeem - > > > > > On May 10, 2023, at 3:09 PM, Azeem Shaikh 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(). > > > No return values were used, so direct replacement is safe. > > > > Actually netid should use the __string() and __assign_str() > > macros rather than open-coding a string copy, I think. > > Ah, hm, yeah, this is tracing wrappers. > > Steve, is there a reason __assign_str() is using "strcpy" and not > strscpy()? Yes. Because __assign_str() predates strscpy() ;-) Note, to use __assign_str(), you first need to do __string(), which will do (in all that TRACE_EVENT() macro magic): #undef __dynamic_array #define __dynamic_array(type, item, len) \ __item_length = (len) * sizeof(type); \ __data_offsets->item = __data_size + \ offsetof(typeof(*entry), __data); \ __data_offsets->item |= __item_length << 16; \ __data_size += __item_length; #undef __string #define __string(item, src) __dynamic_array(char, item, \ strlen((src) ? (const char *)(src) : "(null)") + 1) In order to save a dynamic size string (or array) it must first calculate that size with a strlen(). If the source is not terminated, then this will crash there regardless. The strlen() is to know how much to allocate on the ring buffer, then a copy is done to copy it. I guess you could be worried about the size "changing" between the time it is allocated and copied. If that's the concern then we could do a length copy. > > > Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint") > > Yeah, that works. I was on the fence about adding Fixes for these kinds > of refactoring. Like, it's not really _broken_; we're just trying to > remove the API. > > > > Signed-off-by: Azeem Shaikh > > > --- > > > fs/nfsd/trace.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h > > > index 4183819ea082..9b32cda54808 100644 > > > --- a/fs/nfsd/trace.h > > > +++ b/fs/nfsd/trace.h > > > @@ -1370,7 +1370,7 @@ TRACE_EVENT(nfsd_cb_setup, > > > TP_fast_assign( > > > __entry->cl_boot = clp->cl_clientid.cl_boot; > > > __entry->cl_id = clp->cl_clientid.cl_id; > > > - strlcpy(__entry->netid, netid, sizeof(__entry->netid)); > > > + strscpy(__entry->netid, netid, sizeof(__entry->netid)); > > > __entry->authflavor = authflavor; > > > __assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr, > > > clp->cl_cb_conn.cb_addrlen) > > Leaving code context for Steve to see... > The above isn't __assign_str(). Not exactly sure what you want me to see here. -- Steve