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,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=ham 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 6CDE3C433ED for ; Mon, 17 May 2021 19:49:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C4EB61285 for ; Mon, 17 May 2021 19:49:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235333AbhEQTu3 (ORCPT ); Mon, 17 May 2021 15:50:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235119AbhEQTu2 (ORCPT ); Mon, 17 May 2021 15:50:28 -0400 Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8275C061573 for ; Mon, 17 May 2021 12:49:11 -0700 (PDT) Received: by mail-qk1-x736.google.com with SMTP id q10so7021395qkc.5 for ; Mon, 17 May 2021 12:49:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=usp.br; s=usp-google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=TRWUWGQOzy6Gx8UL2hpuSzK/JXn/cIj3K4kcMXr/CAg=; b=S+iGu4oyeziiCe8xSnBCTcePHgozKkqwLZESh58Mqwa8i6Vr6/lVWRz1XQk5Q/ryDW IrXzwvmJIZ6A3ZV14l1+plNGe10ycyq93hvQPA2M5A/2aL8xcj/UHzzPaavMWqocB20K Mvj7nohJjQQg4ShONTS+FHyL/CKQq/bBwiLSlkgnChF3EPdm+uUV5/bCpsAsJ7rmjF5S UqURHuPGD1zYYwrKAOYJdAN4ofNvIZBzK8lqH6rL7HUzZZ6fPaKxpOwCwjXzqUgXHVLX nkiM18XOWx4dJlp155HhflU9LXDMK6N+UHihxTWLfGli1oJRHJ9c6AdPJTN2BYnssp8g 2ikg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=TRWUWGQOzy6Gx8UL2hpuSzK/JXn/cIj3K4kcMXr/CAg=; b=OqxhJT4Rw9NO1aAklKhT9Im9ltB1Njky+t8PQY4eKbJLWaguUyMgtGikjyoPBU1t42 862NEOPSF/C04Ht0zhIDQhD4XDTi/qUjlLcBCZMlMvRYIsj1WzWs8THG/Db6gn1kd3kV FdGL90kda01K8tGpvfP3iWf3kXQmFoYg0YZLXSOgu7W4vYwYDKvSAoXaxpraOKfqqmyq KLRzgZClcFEBKM7Mv0t0iFe+wYyxPahoIa3yZ41gW3fsZVfsxnTl7p6ZtVm5k7iTIu7Y Q3gCnBicdWN38H7yowPHBWlWW7WnooXBpLC7IA6ZnJPx2cmKU8R3eCagV9oWo7o27t+m 9+uA== X-Gm-Message-State: AOAM532+y1927FIsNAylPM/lPQwjNgSZajfalR6KwZQ4RL8/kSJt7iq9 ajg7P6Bmf3LfqJLVThmLg9q15GYy3HBVqA== X-Google-Smtp-Source: ABdhPJx+KTVFo46UM2Xzk4nPZ53lkPKPBY0nBOcV/Vcw9Vc1Jhlap0+F9ARAPFfeAeJsOMjZ52pgRw== X-Received: by 2002:a05:620a:13ac:: with SMTP id m12mr1563023qki.77.1621280950934; Mon, 17 May 2021 12:49:10 -0700 (PDT) Received: from mango.meuintelbras.local ([177.32.118.149]) by smtp.gmail.com with ESMTPSA id f127sm11174822qkd.81.2021.05.17.12.49.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 May 2021 12:49:10 -0700 (PDT) From: Matheus Tavares To: gitster@pobox.com Cc: git@vger.kernel.org, sandals@crustytoothpaste.net, stolee@gmail.com Subject: [PATCH v2] parallel-checkout: send the new object_id algo field to the workers Date: Mon, 17 May 2021 16:49:03 -0300 Message-Id: <4e113550d595925e4f458cdcb63c7d90205b389b.1621280649.git.matheus.bernardino@usp.br> X-Mailer: git-send-email 2.30.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org An object_id storing a SHA-1 name has some unused bytes at the end of the hash array. Since these bytes are not used, they are usually not initialized to any value either. However, at parallel_checkout.c:send_one_item() the object_id of a cache entry is copied into a buffer which is later sent to a checkout worker through a pipe write(). This makes Valgrind complain about passing uninitialized bytes to a syscall. The worker won't use these uninitialized bytes either, but the warning could confuse someone trying to debug this code; So instead of using oidcpy(), send_one_item() uses hashcpy() to only copy the used/initialized bytes of the object_id, and leave the remaining part with zeros. However, since cf0983213c ("hash: add an algo member to struct object_id", 2021-04-26), using hashcpy() is no longer sufficient here as it won't copy the new algo field from the object_id. Let's add and use a new function which meets both our requirements of copying all the important object_id data while still avoiding the uninitialized bytes, by padding the end of the hash array in the destination object_id. With this change, we also no longer need the destination buffer from send_one_item() to be initialized with zeros, so let's switch from xcalloc() to xmalloc() to make this clear. Signed-off-by: Matheus Tavares --- There is no change since v1, I'm just dropping the RFC status :) hash.h | 16 ++++++++++++++++ parallel-checkout.c | 13 ++++++------- 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/hash.h b/hash.h index 2986f991c6..9c6df4d952 100644 --- a/hash.h +++ b/hash.h @@ -263,6 +263,22 @@ static inline void oidcpy(struct object_id *dst, const struct object_id *src) dst->algo = src->algo; } +/* Like oidcpy() but zero-pads the unused bytes in dst's hash array. */ +static inline void oidcpy_with_padding(struct object_id *dst, + struct object_id *src) +{ + size_t hashsz; + + if (!src->algo) + hashsz = the_hash_algo->rawsz; + else + hashsz = hash_algos[src->algo].rawsz; + + memcpy(dst->hash, src->hash, hashsz); + memset(dst->hash + hashsz, 0, GIT_MAX_RAWSZ - hashsz); + dst->algo = src->algo; +} + static inline struct object_id *oiddup(const struct object_id *src) { struct object_id *dst = xmalloc(sizeof(struct object_id)); diff --git a/parallel-checkout.c b/parallel-checkout.c index 6b1af32bb3..ddc0ff3c06 100644 --- a/parallel-checkout.c +++ b/parallel-checkout.c @@ -411,7 +411,7 @@ static void send_one_item(int fd, struct parallel_checkout_item *pc_item) len_data = sizeof(struct pc_item_fixed_portion) + name_len + working_tree_encoding_len; - data = xcalloc(1, len_data); + data = xmalloc(len_data); fixed_portion = (struct pc_item_fixed_portion *)data; fixed_portion->id = pc_item->id; @@ -421,13 +421,12 @@ static void send_one_item(int fd, struct parallel_checkout_item *pc_item) fixed_portion->name_len = name_len; fixed_portion->working_tree_encoding_len = working_tree_encoding_len; /* - * We use hashcpy() instead of oidcpy() because the hash[] positions - * after `the_hash_algo->rawsz` might not be initialized. And Valgrind - * would complain about passing uninitialized bytes to a syscall - * (write(2)). There is no real harm in this case, but the warning could - * hinder the detection of actual errors. + * We pad the unused bytes in the hash array because, otherwise, + * Valgrind would complain about passing uninitialized bytes to a + * write() syscall. The warning doesn't represent any real risk here, + * but it could hinder the detection of actual errors. */ - hashcpy(fixed_portion->oid.hash, pc_item->ce->oid.hash); + oidcpy_with_padding(&fixed_portion->oid, &pc_item->ce->oid); variant = data + sizeof(*fixed_portion); if (working_tree_encoding_len) { -- 2.30.1