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, URIBL_BLOCKED,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 48620C4741F for ; Thu, 29 Oct 2020 22:37:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF32D2076B for ; Thu, 29 Oct 2020 22:37:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dnxy95AU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725926AbgJ2Wha (ORCPT ); Thu, 29 Oct 2020 18:37:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725868AbgJ2Wh3 (ORCPT ); Thu, 29 Oct 2020 18:37:29 -0400 Received: from mail-qk1-x749.google.com (mail-qk1-x749.google.com [IPv6:2607:f8b0:4864:20::749]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18FB3C0613D3 for ; Thu, 29 Oct 2020 15:37:29 -0700 (PDT) Received: by mail-qk1-x749.google.com with SMTP id f9so2737915qkg.13 for ; Thu, 29 Oct 2020 15:37:29 -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=BiCPGNHEYq7IED6pRZ/BzCt1AxbVwIiK4WTDKoCvHSM=; b=dnxy95AUQmjaY8Bv8LSaCRLQqP0eaMVA7DHEhwQJSsLrrv5iYturZZMke2JunjNxWs Crh95X5tigSC6Y9q3VS175Ihr8AEZxaJKKUjvlh19VOPVXKwuZqPYEQvqmJ05tL07jPy Te68NYUPjuK845g+oAbUVgeef6XVgBN8rTMmFWRDrDcnsPWBFY8CmLz3VGvDBgF3K/8f l2QzEtpWq/7e/JgQFf8luCGNrtql8MmZ6jkPpZVwHK25ERtw+C9ME61Ort0Ax4hDnR2f y6x+xvlKUJ3MS5QNt0QdwG50c/CH3ND4BqD8ON0IjQMmh+fpY8uXOfKt9mcNPUtS6y33 Pe1Q== 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=BiCPGNHEYq7IED6pRZ/BzCt1AxbVwIiK4WTDKoCvHSM=; b=fi93fwcRS/VL6+nU8fWmNFfPogXfo3s8wWMi10ryNabaMOuFZfAKI/+BWbAZo0xGCx v8ALkXosErH5j/ww03SPCRQJR71yhKc0rMVwSl+Pat2F2nnQT2bx30DVFclbtAu9t4rM 1WVlP8oUPCkwC8y2WEgCTeO0ockcxRZ7qgTlyOIg1pPZX3crPx2OjP18UXmi+hu8UK5g B87R9AA+AcjemCC640TskVOuska4IRVo0B5ZyADwdvjwkE530gqs57E/xO7oERtLTG4/ 3fK6BSMfpP44RSdaXxlyUa0LRhD1zXXDF3uZ5XvadzVfTi4MBV52udSiV+0w451j0uLp JT1A== X-Gm-Message-State: AOAM533+jZqcgjK6Cvpo5K4IpX9axvH/dw7aTO/0wtVORnrK1PdWaoul OoZj8S4opLufrZlJFzaGPVPacVlO7i/1 X-Google-Smtp-Source: ABdhPJxWrWDS38PkkbgZk9b4i52L8CEXtkQ8bJSOEdv/nw+U1dByIV6meridJeVbYTlItASPFe201nMxl5oZ 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:ad4:43ca:: with SMTP id o10mr6868463qvs.33.1604011048079; Thu, 29 Oct 2020 15:37:28 -0700 (PDT) Date: Thu, 29 Oct 2020 15:37:07 -0700 Message-Id: <20201029223707.494059-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.29.1.341.ge80a0c044ae-goog Subject: [PATCH v2] 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 and guarding calls to hash_bits for empty maps in hashmap__for_each_key_entry and hashmap__for_each_entry_safe. Suggested-by: Andrii Nakryiko , Signed-off-by: Ian Rogers --- tools/lib/bpf/hashmap.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h index d9b385fe808c..10a4c4cd13cf 100644 --- a/tools/lib/bpf/hashmap.h +++ b/tools/lib/bpf/hashmap.h @@ -15,6 +15,9 @@ static inline size_t hash_bits(size_t h, int bits) { /* shuffle bits and return requested number of upper bits */ + if (bits == 0) + return 0; + #if (__SIZEOF_SIZE_T__ == __SIZEOF_LONG_LONG__) /* LP64 case */ return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits); @@ -174,17 +177,17 @@ bool hashmap__find(const struct hashmap *map, const void *key, void **value); * @key: key to iterate entries for */ #define hashmap__for_each_key_entry(map, cur, _key) \ - for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\ - map->cap_bits); \ - map->buckets ? map->buckets[bkt] : NULL; }); \ + for (cur = map->buckets \ + ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \ + : NULL; \ cur; \ cur = cur->next) \ if (map->equal_fn(cur->key, (_key), map->ctx)) #define hashmap__for_each_key_entry_safe(map, cur, tmp, _key) \ - for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\ - map->cap_bits); \ - cur = map->buckets ? map->buckets[bkt] : NULL; }); \ + for (cur = map->buckets \ + ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \ + : NULL; \ cur && ({ tmp = cur->next; true; }); \ cur = tmp) \ if (map->equal_fn(cur->key, (_key), map->ctx)) -- 2.29.1.341.ge80a0c044ae-goog