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 7DB7BC3F6B0 for ; Tue, 23 Aug 2022 21:58:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229963AbiHWV6o (ORCPT ); Tue, 23 Aug 2022 17:58:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229622AbiHWV6n (ORCPT ); Tue, 23 Aug 2022 17:58:43 -0400 Received: from smtp-fw-33001.amazon.com (smtp-fw-33001.amazon.com [207.171.190.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6CEF959C; Tue, 23 Aug 2022 14:58:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1661291922; x=1692827922; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=P2sg/Y2ei1LJ5TOzsXWJG6dJ7t5e5k6b+DFks6T66ZI=; b=egqtrGlOdeCOyz1VycYEPRl9aBRn0ArUIfhu5qZNX3ygmWz9IvBboDAI omYCOegSU6AAci/yyfs4BQKeh7mD9AuVSTACJ3I7meJfROViIp2sZSX41 FnLraZlMJJ+gEQFnyDdr7EQaIqlQuaaBokBFBFXy+Q49bLVVOKRs3NE5j Y=; X-IronPort-AV: E=Sophos;i="5.93,258,1654560000"; d="scan'208";a="220438679" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-pdx-2a-5feb294a.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-33001.sea14.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2022 21:58:26 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-pdx-2a-5feb294a.us-west-2.amazon.com (Postfix) with ESMTPS id 78FD581A39; Tue, 23 Aug 2022 21:58:25 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.249) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Tue, 23 Aug 2022 21:58:24 +0000 Received: from 88665a182662.ant.amazon.com (10.43.162.140) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.12; Tue, 23 Aug 2022 21:58:22 +0000 From: Kuniyuki Iwashima To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko CC: Kuniyuki Iwashima , Kuniyuki Iwashima , , Subject: [PATCH v3 bpf] bpf: Fix a data-race around bpf_jit_limit. Date: Tue, 23 Aug 2022 14:58:04 -0700 Message-ID: <20220823215804.2177-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.43.162.140] X-ClientProxiedBy: EX13D47UWC003.ant.amazon.com (10.43.162.70) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org While reading bpf_jit_limit, it can be changed concurrently via sysctl, WRITE_ONCE() in __do_proc_doulongvec_minmax(). The size of bpf_jit_limit is long, so we need to add a paired READ_ONCE() to avoid load-tearing. Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations") Signed-off-by: Kuniyuki Iwashima --- v3: * Update changelog to clarify paired WRITE_ONCE() and motivation as load-tearing. v2: https://lore.kernel.org/netdev/20220823181247.90349-1-kuniyu@amazon.com/ * Drop other 3 patches (No change for this patch) v1: https://lore.kernel.org/bpf/20220818042339.82992-1-kuniyu@amazon.com/ --- kernel/bpf/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index c1e10d088dbb..3d9eb3ae334c 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -971,7 +971,7 @@ pure_initcall(bpf_jit_charge_init); int bpf_jit_charge_modmem(u32 size) { - if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) { + if (atomic_long_add_return(size, &bpf_jit_current) > READ_ONCE(bpf_jit_limit)) { if (!bpf_capable()) { atomic_long_sub(size, &bpf_jit_current); return -EPERM; -- 2.30.2