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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 198DEC43603 for ; Tue, 2 Mar 2021 04:43:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E60F86148E for ; Tue, 2 Mar 2021 04:43:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1443253AbhCBCUE (ORCPT ); Mon, 1 Mar 2021 21:20:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:55154 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241721AbhCATq0 (ORCPT ); Mon, 1 Mar 2021 14:46:26 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1CFCC652E1; Mon, 1 Mar 2021 17:39:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614620366; bh=NgyCZmuYOTuc8kjm1KjUZenqnDmxnQHGJ2KI7vihzrc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Pm6rIgf73onMmD0kxykEcoCy1gF4nCw+WKADrPGXmG3G/Pwq5Gj9pN5lgp7UzoEUf O/H7LFR0Q7lalOLCPXoTtJevqzNXmeZubZzD5TrSFPEyVmi/Hz69zEo6JSkIogCnh3 59p26BoCKr2nEW2vc2WQXqM9PcuiLb2Vlh7mVgl0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yauheni Kaliuta , Ilya Leoshkevich , Daniel Borkmann , Sasha Levin Subject: [PATCH 5.11 127/775] bpf: Clear subreg_def for global function return values Date: Mon, 1 Mar 2021 17:04:55 +0100 Message-Id: <20210301161207.953525968@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ilya Leoshkevich [ Upstream commit 45159b27637b0fef6d5ddb86fc7c46b13c77960f ] test_global_func4 fails on s390 as reported by Yauheni in [1]. The immediate problem is that the zext code includes the instruction, whose result needs to be zero-extended, into the zero-extension patchlet, and if this instruction happens to be a branch, then its delta is not adjusted. As a result, the verifier rejects the program later. However, according to [2], as far as the verifier's algorithm is concerned and as specified by the insn_no_def() function, branching insns do not define anything. This includes call insns, even though one might argue that they define %r0. This means that the real problem is that zero extension kicks in at all. This happens because clear_caller_saved_regs() sets BPF_REG_0's subreg_def after global function calls. This can be fixed in many ways; this patch mimics what helper function call handling already does. [1] https://lore.kernel.org/bpf/20200903140542.156624-1-yauheni.kaliuta@redhat.com/ [2] https://lore.kernel.org/bpf/CAADnVQ+2RPKcftZw8d+B1UwB35cpBhpF5u3OocNh90D9pETPwg@mail.gmail.com/ Fixes: 51c39bb1d5d1 ("bpf: Introduce function-by-function verification") Reported-by: Yauheni Kaliuta Signed-off-by: Ilya Leoshkevich Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210212040408.90109-1-iii@linux.ibm.com Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 20babdd06278f..33683eafea90e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4834,8 +4834,9 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn, subprog); clear_caller_saved_regs(env, caller->regs); - /* All global functions return SCALAR_VALUE */ + /* All global functions return a 64-bit SCALAR_VALUE */ mark_reg_unknown(env, caller->regs, BPF_REG_0); + caller->regs[BPF_REG_0].subreg_def = DEF_NOT_SUBREG; /* continue with next insn after call */ return 0; -- 2.27.0