From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D262212F98; Wed, 29 Oct 2025 16:40:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761756043; cv=none; b=hoFuDvJguqXOR6TTftRrcOWhQG77nS/uuMCWHiGznXcCqkbe8tcwlgoggp0ein0M7nlClkhWeSrs7SpTMCaDSkiTLuz+N3Sn0pETMFxyOKBmm89HU0ZTdb2QlI8fPeCNlU/PlYXVAG2wg3jA+aQ3N493G8FeLjY06pRMuFg4znQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761756043; c=relaxed/simple; bh=OxUOwbrpCvF0HAEQwSURb7tpIIOXs+l5SN/iqW9Rcgw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=D9BtpxD/RaiHEYhNFd6WSlqs76X1pUPkD65Y/qQA2OvhtT2yJXm9B8GEdfkisIl03VtD8slxEF3oxW6JehFetd4HjRHF5S+NaEwmvAhJuE2x12nJCRx0w9A498AJjfCspQXJ0qWnWuuwm2fo2VoJOZDJkCg8xOOQt1+gENw/AG0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VOBbTUuR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VOBbTUuR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29A2AC4CEF7; Wed, 29 Oct 2025 16:40:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761756043; bh=OxUOwbrpCvF0HAEQwSURb7tpIIOXs+l5SN/iqW9Rcgw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VOBbTUuRHOBE1Si9/iKOvYdtrYaI04/EXzOV4MmJIhN8DY/hsUfxhKG2fjXfmQH7U aQoqBTJwlKsAjBrXWHmuDv05s2mdSG8kMhp12mXDZznf1GriIxG3wDkfqW5jBimDvd hfYSZOdRnkyIrSbi+WzsLV7Vnn0NUntjn529W41ivXSzKgiGpYVNdLIpIsDzVLhDGr RUYrv+RyatFkj9yFEnfGDDCiv7d9IuKubNOitwUMI3vNSaQJ5KKsrGLbCVLNHDyaox zARUQ6O0qvphxqYMqo00iDUBhXXcJthWqAjHnkxcV2CFKBQ8zkaHnyn1vuVGQItNwC 8Z3BKfONtFrNA== Date: Wed, 29 Oct 2025 16:40:38 +0000 From: Simon Horman To: Stefan Wiehler Cc: Xin Long , "David S . Miller " , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Kuniyuki Iwashima , linux-sctp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v3 1/3] sctp: Hold RCU read lock while iterating over address list Message-ID: References: <20251028161506.3294376-1-stefan.wiehler@nokia.com> <20251028161506.3294376-2-stefan.wiehler@nokia.com> Precedence: bulk X-Mailing-List: linux-sctp@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Oct 29, 2025 at 04:38:44PM +0000, Simon Horman wrote: > On Tue, Oct 28, 2025 at 05:12:26PM +0100, Stefan Wiehler wrote: > > With CONFIG_PROVE_RCU_LIST=y and by executing > > > > $ netcat -l --sctp & > > $ netcat --sctp localhost & > > $ ss --sctp > > > > one can trigger the following Lockdep-RCU splat(s): > > ... > > > diff --git a/net/sctp/diag.c b/net/sctp/diag.c > > index 996c2018f0e6..1a8761f87bf1 100644 > > --- a/net/sctp/diag.c > > +++ b/net/sctp/diag.c > > @@ -73,19 +73,23 @@ static int inet_diag_msg_sctpladdrs_fill(struct sk_buff *skb, > > struct nlattr *attr; > > void *info = NULL; > > > > + rcu_read_lock(); > > list_for_each_entry_rcu(laddr, address_list, list) > > addrcnt++; > > + rcu_read_unlock(); > > > > attr = nla_reserve(skb, INET_DIAG_LOCALS, addrlen * addrcnt); > > if (!attr) > > return -EMSGSIZE; > > > > info = nla_data(attr); > > Hi Stefan, > > If the number of entries in list increases while rcu_read_lock is not held, > between when addrcnt is calculated and when info is written, then can an > overrun occur while writing info? Oops, I now see that is addressed in patch 2/3. Sorry for not reading that before sending my previous email. > > > + rcu_read_lock(); > > list_for_each_entry_rcu(laddr, address_list, list) { > > memcpy(info, &laddr->a, sizeof(laddr->a)); > > memset(info + sizeof(laddr->a), 0, addrlen - sizeof(laddr->a)); > > info += addrlen; > > } > > + rcu_read_unlock(); > > > > return 0; > > } > > -- > > 2.51.0 > >