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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D238C2D0E5 for ; Thu, 26 Mar 2020 15:52:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6398220787 for ; Thu, 26 Mar 2020 15:52:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZpNCpuWZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727939AbgCZPw0 (ORCPT ); Thu, 26 Mar 2020 11:52:26 -0400 Received: from mail-pj1-f67.google.com ([209.85.216.67]:53531 "EHLO mail-pj1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727733AbgCZPw0 (ORCPT ); Thu, 26 Mar 2020 11:52:26 -0400 Received: by mail-pj1-f67.google.com with SMTP id l36so2637237pjb.3; Thu, 26 Mar 2020 08:52:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-transfer-encoding; bh=Cu2h+YcrIqDJjOVWrcg9qh9LpRYfxDF53j5qt17OgDg=; b=ZpNCpuWZ1eSy5xaFqAzytGomXpY7T6zoCAEDuqCdM/QnB8FEHI+Np/oVS8KtCcplt6 Nw3z8OSJ6Ns2Gxv+36EFFbxc7cdWM7+3MOLTvhCwvIFVryOst5CRoVr500EcYGcJn0GH EGoW3jmYYml74SyfKTAkCzs1vRup5X2cJHpiNUzuDnD+VRVG6V6IrPb4yN1Z18s3kFd9 VzSAKjzG9Ex4qzgywFX+B1Ildm0SQDwLgRF4RyTg3DLTMDjjPPnsBLzYw9SxWjKo0U4n 5Hx8+3QqWFNxUeYmEFGs/qpDWUWhbffJOPwzzD1/g76i7s2hwMO41+DBFtbTzjanUwk4 t22g== 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:message-id:in-reply-to :references:subject:mime-version:content-transfer-encoding; bh=Cu2h+YcrIqDJjOVWrcg9qh9LpRYfxDF53j5qt17OgDg=; b=Yd7lRRh5Q6Z8gXT4/vhBNrhmVGdBpuVIsUzUupBEieadTaF3CXjcaaRKJhtQsFtty0 kJHokwnY9DQMRoKCVzzqsiHkqPcaUHTzPxUX4bHiwlb0Ibdkep7L+3gzdLdcXbGZ7Bqe 3O0LSu9P1MBGbcM647yLwKn/81OcUOOrUO7acmQQluiGbeaeJLuOPLDrFXO4qzmhkOVL 7ox1PIsGXrOgSvNtBAJCMwUk/MKJedYiYv9GxsHyc+ZAmr9HrgDSNIgkAzdfKvzN20Q6 JkGfKM2Utug0iYB/Zsm/LDvt06giJf3akzGuDfeAQSN4xFYvCiKwtqi9cYufdeEm9Jn1 JDfg== X-Gm-Message-State: ANhLgQ1wb+EdFBccXAk3fLarTZphbIuzJ58LFZaJD0NeexqA/WTOiY32 DQJFkQ3m5zq5OqJ2tQc42Gc= X-Google-Smtp-Source: ADFU+vvobQjrEUNfhNe6x6YveJ/MhPXKkPyTF2aUoNHOWe2uLqdm9w4HnO6hFY7KULhNtPblAlBe3Q== X-Received: by 2002:a17:902:b40e:: with SMTP id x14mr8090137plr.319.1585237945470; Thu, 26 Mar 2020 08:52:25 -0700 (PDT) Received: from localhost ([184.63.162.180]) by smtp.gmail.com with ESMTPSA id g30sm1956366pgn.40.2020.03.26.08.52.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 08:52:24 -0700 (PDT) Date: Thu, 26 Mar 2020 08:52:15 -0700 From: John Fastabend To: Alexei Starovoitov , John Fastabend Cc: ecree@solarflare.com, yhs@fb.com, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Message-ID: <5e7ccfaf79433_65132acbbe7fc5c4eb@john-XPS-13-9370.notmuch> In-Reply-To: <20200326062301.fvomwkz5grg3b5qb@ast-mbp> References: <158507130343.15666.8018068546764556975.stgit@john-Precision-5820-Tower> <158507155667.15666.4189866174878249746.stgit@john-Precision-5820-Tower> <20200326062301.fvomwkz5grg3b5qb@ast-mbp> Subject: Re: [bpf-next PATCH 05/10] bpf: verifier, return value is an int in do_refine_retval_range Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Alexei Starovoitov wrote: > On Tue, Mar 24, 2020 at 10:39:16AM -0700, John Fastabend wrote: > > Mark 32-bit subreg region with max value because do_refine_retval_range() > > catches functions with int return type (We will assume here that int is > > a 32-bit type). Marking 64-bit region could be dangerous if upper bits > > are not zero which could be possible. > > > > Two reasons to pull this out of original patch. First it makes the original > > fix impossible to backport. And second I've not seen this as being problematic > > in practice unlike the other case. > > > > Fixes: 849fa50662fbc ("bpf/verifier: refine retval R0 state for bpf_get_stack helper") > > Signed-off-by: John Fastabend > > --- > > kernel/bpf/verifier.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 6372fa4..3731109 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -4328,7 +4328,7 @@ static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type, > > func_id != BPF_FUNC_probe_read_str)) > > return; > > > > - ret_reg->smax_value = meta->msize_max_value; > > + ret_reg->s32_max_value = meta->msize_max_value; > > I think this is not correct. > These two special helpers are invoked via BPF_CALL_x() which has u64 return value. > So despite having 'int' return in bpf_helper_defs.h the upper 32-bit will be correct. > I think this patch should do: > ret_reg->smax_value = meta->msize_max_value; > ret_reg->s32_max_value = meta->msize_max_value; OK, I missed the u64 in BPF_CALL_x(). Setting both smax and s32_max looks correct. My logic above is wrong so I'll fix that. Thanks.