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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 052E9C2D0A3 for ; Thu, 29 Oct 2020 16:09:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BF5C2076E for ; Thu, 29 Oct 2020 16:09:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TkD7sB+l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726203AbgJ2QJr (ORCPT ); Thu, 29 Oct 2020 12:09:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725784AbgJ2QJp (ORCPT ); Thu, 29 Oct 2020 12:09:45 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDCD1C0613D2 for ; Thu, 29 Oct 2020 09:09:43 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id o11so1025987pgj.21 for ; Thu, 29 Oct 2020 09:09:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=M5ZYnY3+Esbb7Wzf3rbFgZzcgHLDPaDcLNV16K0VsQk=; b=TkD7sB+lP2yjvB0Gn0LUz1ZODCeWbb3o5+lnejOZhE+jvkt4r05YDH3rPa98mrHJ2C KXmSJyYJ57SAGMkmu/Z0F7JDtTXTG2GCkITcGFpmImYXiyrwTpSBlN9fNZMYyXRFMeIy AgEzX+9j08TZDbrZs4O0e2qGpPHAhU0mNA9AYKmXoqQg+1/zlQ0h6N0DlJUMXP0yN1cL Hk7ywZGSyVsXhivYWHj4aZ6lE/LguaopaSvmTW1vVdphKsbV9sTvx0HxpMe0n/4BTTKC 4dgK1V1IizyRITrQLKfjBsdmQHqr8sBSXvFk/WUmaMzzypabYkwcGX7NktWevFA/hBBs mNsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=M5ZYnY3+Esbb7Wzf3rbFgZzcgHLDPaDcLNV16K0VsQk=; b=PMsKZTq210PsoppBnjNWc+C5GRvYOpPmiq12P1COfnXgHwMYTQr8uy3ud5K3FJmuNM QVP2V3ds9Ev/xy6/tGR3XWT6P35qF+ZjIAr9AtZvxfzUy3NS6fD31o0lT/7AmthWfkz6 wDFby9ACmYzY6czmIkBpR0sKhgP3oFDXUlwUaE26Nv9PKQQ4iYOj+AKEJvR6rpuCHeZZ 1EZO1e2tkykEExyWOtDLY1p68f5J4dgHy8PsosulbuNzbrdu2GucXRkSo8QT3styxd0P N40J2VjeryVYyU4tcM3G9rzHwubCCc0T3r0VL+5iHKjmf205FMF0Jh3DkEQqZz1EAVH9 r/yg== X-Gm-Message-State: AOAM533AIji++yuuc7govjA0cYBPSXTmfc4akdolzCjYxc4+T0dJiiog gDMd13wxYmbSn/9HScSYQXnJ4BK6XJXw X-Google-Smtp-Source: ABdhPJxxxja0byw0woovLqKs/U5wkLuHYPqEf0rerA1ne8mXTfKCoHV8TAnXpLkAJj3iQyXXo0gccX84HqgW Sender: "irogers via sendgmr" X-Received: from irogers.svl.corp.google.com ([2620:15c:2cd:2:f693:9fff:fef4:4583]) (user=irogers job=sendgmr) by 2002:a62:3815:0:b029:152:80d4:2a6f with SMTP id f21-20020a6238150000b029015280d42a6fmr5004920pfa.72.1603987783316; Thu, 29 Oct 2020 09:09:43 -0700 (PDT) Date: Thu, 29 Oct 2020 09:09:38 -0700 Message-Id: <20201029160938.154084-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.29.1.341.ge80a0c044ae-goog Subject: [PATCH] libbpf hashmap: Fix undefined behavior in hash_bits From: Ian Rogers To: Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Ian Rogers Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If bits is 0, the case when the map is empty, then the >> is the size of the register which is undefined behavior - on x86 it is the same as a shift by 0. Fix by handling the 0 case explicitly when running with address sanitizer. A variant of this patch was posted previously as: https://lore.kernel.org/lkml/20200508063954.256593-1-irogers@google.com/ Signed-off-by: Ian Rogers --- tools/lib/bpf/hashmap.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h index d9b385fe808c..27d0556527d3 100644 --- a/tools/lib/bpf/hashmap.h +++ b/tools/lib/bpf/hashmap.h @@ -12,9 +12,23 @@ #include #include +#ifdef __has_feature +#define HAVE_FEATURE(f) __has_feature(f) +#else +#define HAVE_FEATURE(f) 0 +#endif + static inline size_t hash_bits(size_t h, int bits) { /* shuffle bits and return requested number of upper bits */ +#if defined(ADDRESS_SANITIZER) || HAVE_FEATURE(address_sanitizer) + /* + * If the requested bits == 0 avoid undefined behavior from a + * greater-than bit width shift right (aka invalid-shift-exponent). + */ + if (bits == 0) + return -1; +#endif #if (__SIZEOF_SIZE_T__ == __SIZEOF_LONG_LONG__) /* LP64 case */ return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits); -- 2.29.1.341.ge80a0c044ae-goog