From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f172.google.com (mail-pl1-f172.google.com [209.85.214.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F44470 for ; Wed, 28 Jul 2021 18:57:16 +0000 (UTC) Received: by mail-pl1-f172.google.com with SMTP id c16so3829356plh.7 for ; Wed, 28 Jul 2021 11:57:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=127Od1Z5L5mrPERJlQTktPz34XXJuvOrvHqT3KKh12Q=; b=CT/CUy6V11s/6KhYMzSsdsMDErLudpJAHUqNC0Rpu9F7Ero2CNsiQemV80Kh7YxA18 O09bddDAkQD5N79FTWd2JhufucZWJdvUnGQK4C3MDdI6o+fliBhy2PpoYHcWAEFN4pot mlS6O/Te+d+/T7xLqqDiIN6UOLBL2XxRO5jCQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=127Od1Z5L5mrPERJlQTktPz34XXJuvOrvHqT3KKh12Q=; b=KpIrbP3EdsII3K4/0fomlnus1OSF+CljQVILQLvbOE3ErGRH8Mnh6fLMofn5Gq4xAA rIR4Ie7bZ9+Fjw5fm7NybtqNdUKZtku+2Y2iNjHmW3Z3jkdBpEAHGj3Edo+GOKwgoFhI Tr/xMtz081UVy0YMiSaG5W7DsBdSdyh0kyHxU26T2iQlBHNNXy4kiHktgwwtghdhKjJd huJX9pshEuCTTonJaiCVmgfy9vT+xvipT7qvRFmuitAeVjp6BecvmUIVSs+h9osoigGa XMxIDsYKgwCVLocP2MBDba2Jl8sKL7NNznIG/yo8MGLCpHK6J9LpvyMYpTkrJ2GcjEGl PIYQ== X-Gm-Message-State: AOAM533uJIzlcOp4k6U6CUPf2nmC/T3o0unwvu+pjHewS6jCy6APvH5l icQ7Nfx6LSwBA4XsSTvNG0aJ8A== X-Google-Smtp-Source: ABdhPJznHpu/gslPhcK+chR4/yRixyO0Zt/1nxlU5ZOnQ6g7gqNYFE0PSpANagAqHnwDfuJHc+ddvw== X-Received: by 2002:a63:4c26:: with SMTP id z38mr313058pga.376.1627498636621; Wed, 28 Jul 2021 11:57:16 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id d14sm5792859pjc.0.2021.07.28.11.57.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jul 2021 11:57:16 -0700 (PDT) Date: Wed, 28 Jul 2021 11:57:15 -0700 From: Kees Cook To: "Martin K. Petersen" Cc: linux-hardening@vger.kernel.org, "Gustavo A. R. Silva" , Keith Packard , Greg Kroah-Hartman , Andrew Morton , linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, Brian King , Tyrel Datwyler Subject: Re: [PATCH 36/64] scsi: ibmvscsi: Avoid multi-field memset() overflow by aiming at srp Message-ID: <202107281152.515A3BA@keescook> References: <20210727205855.411487-1-keescook@chromium.org> <20210727205855.411487-37-keescook@chromium.org> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jul 27, 2021 at 09:39:39PM -0400, Martin K. Petersen wrote: > > Kees, > > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > field bounds checking for memset(), avoid intentionally writing across > > neighboring fields. > > > > Instead of writing beyond the end of evt_struct->iu.srp.cmd, target the > > upper union (evt_struct->iu.srp) instead, as that's what is being wiped. > > > > Signed-off-by: Kees Cook > > Orthogonal to your change, it wasn't immediately obvious to me that > SRP_MAX_IU_LEN was the correct length to use for an srp_cmd. However, I > traversed the nested unions and it does look OK. Yeah, I had the same fun. Maybe I should add a BUILD_BUG_ON() here to help illustrate the relationship? I did that in a few other places where the equalities weren't very clear. For example, change it to: + BUILD_BUG_ON(sizeof(evt_struct->iu.srp) != SRP_MAX_IU_LEN); + memset(&evt_struct->iu.srp, 0x00, sizeof(evt_struct->iu.srp)); srp_cmd = &evt_struct->iu.srp.cmd; - memset(srp_cmd, 0x00, SRP_MAX_IU_LEN); > > For good measure I copied Tyrel and Brian. > > Acked-by: Martin K. Petersen For the moment, I'll leave the patch as-is unless you prefer having the BUILD_BUG_ON(). :) Thanks! -Kees > > > --- > > drivers/scsi/ibmvscsi/ibmvscsi.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c > > index e6a3eaaa57d9..7e8beb42d2d3 100644 > > --- a/drivers/scsi/ibmvscsi/ibmvscsi.c > > +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c > > @@ -1055,8 +1055,8 @@ static int ibmvscsi_queuecommand_lck(struct scsi_cmnd *cmnd, > > return SCSI_MLQUEUE_HOST_BUSY; > > > > /* Set up the actual SRP IU */ > > + memset(&evt_struct->iu.srp, 0x00, SRP_MAX_IU_LEN); > > srp_cmd = &evt_struct->iu.srp.cmd; > > - memset(srp_cmd, 0x00, SRP_MAX_IU_LEN); > > srp_cmd->opcode = SRP_CMD; > > memcpy(srp_cmd->cdb, cmnd->cmnd, sizeof(srp_cmd->cdb)); > > int_to_scsilun(lun, &srp_cmd->lun); > > -- > Martin K. Petersen Oracle Linux Engineering -- Kees Cook