From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 6A2E21F670 for ; Fri, 14 Aug 2020 06:00:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726663AbgHNGA1 (ORCPT ); Fri, 14 Aug 2020 02:00:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726139AbgHNGAZ (ORCPT ); Fri, 14 Aug 2020 02:00:25 -0400 Received: from mail-wr1-x42f.google.com (mail-wr1-x42f.google.com [IPv6:2a00:1450:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1DAB0C061757 for ; Thu, 13 Aug 2020 23:00:25 -0700 (PDT) Received: by mail-wr1-x42f.google.com with SMTP id a15so7275562wrh.10 for ; Thu, 13 Aug 2020 23:00:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:in-reply-to:references:from:date:subject:fcc :content-transfer-encoding:mime-version:to:cc; bh=8LqUqVEVgVicP9J80Tv6tj3ufmN52cd6R9aYCtUbcGM=; b=kloSSrIeiNY6xPeiUEQ66/kSSnlYzH9R0BD/uNLaiVv8e3M7FItT2K5yACGyjfcI4K HV6a1/ewLfJy6M/NlmLcYVWm0v1tGd2JCuqW31CdGO1F/OEkVmSgjddWyD7U9wEedTkP v6qOc4OBUg7ObFBrVg/KrCTY3mUwya5r0tlZCYmM8Z6lthyA4OhbTIrM2b1av5lY/Vo4 9E75I88OE/Qg34kLvnkDNo/KiN/9b5lV2Kxr/3Cehy3qc0AdH5yC/k5Z+uykt+XFpiJh LGbf0inOh+HT691QWgn3nacM8Fl119mPub5JqrZ+kR2T5O/ad+yi+MOtJZRXeRSi3Ybn awLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:in-reply-to:references:from:date :subject:fcc:content-transfer-encoding:mime-version:to:cc; bh=8LqUqVEVgVicP9J80Tv6tj3ufmN52cd6R9aYCtUbcGM=; b=icFxxMAf6RA0LawHPT71TSWmRo4izlWM5OTuNoGquZV7WeA21gYpEIX3Ta6oHBcZGz pDXyVmv7fY+xQw9Ufc7/BCUsYhzv6+916pZNiqOxN597Mj8CXtQTCUJ6G9oBLH2ZQtzd zu1/6IZ0ahJ/JIHnuC7Z+miBVHLpKd/i4j4wRzqBz4/1ZMwfO+QSV6Oh85M7GCOH+FZU T3fXBB16JmrM4+BdNt77dYF3q16EiUOxZGxUhFBwYANO2nKRosKwmIhOFjAllpRBryA9 avjV0A0fLbXxmMRBnQnDcM0dUhHvFm1mvEEyGkLny7S/BNQ+ReotOH+3CT1Dvcswvurd Df4Q== X-Gm-Message-State: AOAM532cXygpArR6z3XwK4cCjrVxvMeHGeKjA93rO09KtC8WSC8GQdzZ Hip1Be9LOWEyWZbkwqHYk1FpyYBhCjE= X-Google-Smtp-Source: ABdhPJwc90i3OjOf3sEfWQRxTFbN+jNCXQLQlbUWUyxkLZ2eZtPCGL6qtpqxrwF9xYwbxXHEo8iuTg== X-Received: by 2002:adf:ab05:: with SMTP id q5mr1117882wrc.46.1597384823466; Thu, 13 Aug 2020 23:00:23 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id g18sm13611438wru.27.2020.08.13.23.00.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Aug 2020 23:00:23 -0700 (PDT) Message-Id: In-Reply-To: References: From: "Elijah Newren via GitGitGadget" Date: Fri, 14 Aug 2020 06:00:19 +0000 Subject: [PATCH v2 2/3] mem-pool: use more standard initialization and finalization Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 To: git@vger.kernel.org Cc: Matheus Tavares , Eric Sunshine , Elijah Newren , Elijah Newren Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Elijah Newren A typical memory type, such as strbuf, hashmap, or string_list can be stored on the stack or embedded within another structure. mem_pool cannot be, because of how mem_pool_init() and mem_pool_discard() are written. mem_pool_init() does essentially the following (simplified for purposes of explanation here): void mem_pool_init(struct mem_pool **pool...) { *pool = xcalloc(1, sizeof(*pool)); It seems weird to require that mem_pools can only be accessed through a pointer. It also seems slightly dangerous: unlike strbuf_release() or strbuf_reset() or string_list_clear(), all of which put the data structure into a state where it can be re-used after the call, mem_pool_discard(pool) will leave pool pointing at free'd memory. read-cache (and split-index) are the only current users of mem_pools, and they haven't fallen into a use-after-free mistake here, but it seems likely to be problematic for future users especially since several of the current callers of mem_pool_init() will only call it when the mem_pool* is not already allocated (i.e. is NULL). This type of mechanism also prevents finding synchronization points where one can free existing memory and then resume more operations. It would be natural at such points to run something like mem_pool_discard(pool...); and, if necessary, mem_pool_init(&pool...); and then carry on continuing to use the pool. However, this fails badly if several objects had a copy of the value of pool from before these commands; in such a case, those objects won't get the updated value of pool that mem_pool_init() overwrites pool with and they'll all instead be reading and writing from free'd memory. Modify mem_pool_init()/mem_pool_discard() to behave more like strbuf_init()/strbuf_release() or string_list_init()/string_list_clear() In particular: (1) make mem_pool_init() just take a mem_pool* and have it only worry about allocating struct mp_blocks, not the struct mem_pool itself, (2) make mem_pool_discard() free the memory that the pool was responsible for, but leave it in a state where it can be used to allocate more memory afterward (without the need to call mem_pool_init() again). Signed-off-by: Elijah Newren --- mem-pool.c | 15 ++++----------- mem-pool.h | 4 ++-- read-cache.c | 21 +++++++++++++-------- split-index.c | 6 ++++-- 4 files changed, 23 insertions(+), 23 deletions(-) diff --git a/mem-pool.c b/mem-pool.c index 33fda1c411..305bcd3542 100644 --- a/mem-pool.c +++ b/mem-pool.c @@ -33,21 +33,13 @@ static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t b return p; } -void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size) +void mem_pool_init(struct mem_pool *pool, size_t initial_size) { - struct mem_pool *pool; - - if (*mem_pool) - return; - - pool = xcalloc(1, sizeof(*pool)); - + memset(pool, 0, sizeof(*pool)); pool->block_alloc = BLOCK_GROWTH_SIZE; if (initial_size > 0) mem_pool_alloc_block(pool, initial_size, NULL); - - *mem_pool = pool; } void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory) @@ -66,7 +58,8 @@ void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory) free(block_to_free); } - free(mem_pool); + mem_pool->mp_block = NULL; + mem_pool->pool_alloc = 0; } void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len) diff --git a/mem-pool.h b/mem-pool.h index fcaa2d462b..a55ee4bc38 100644 --- a/mem-pool.h +++ b/mem-pool.h @@ -24,10 +24,10 @@ struct mem_pool { /* * Initialize mem_pool with specified initial size. */ -void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size); +void mem_pool_init(struct mem_pool *pool, size_t initial_size); /* - * Discard a memory pool and free all the memory it is responsible for. + * Discard all the memory the memory pool is responsible for. */ void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory); diff --git a/read-cache.c b/read-cache.c index 8ed1c29b54..fa291cdbee 100644 --- a/read-cache.c +++ b/read-cache.c @@ -89,8 +89,10 @@ static struct mem_pool *find_mem_pool(struct index_state *istate) else pool_ptr = &istate->ce_mem_pool; - if (!*pool_ptr) - mem_pool_init(pool_ptr, 0); + if (!*pool_ptr) { + *pool_ptr = xmalloc(sizeof(**pool_ptr)); + mem_pool_init(*pool_ptr, 0); + } return *pool_ptr; } @@ -2006,11 +2008,12 @@ static unsigned long load_all_cache_entries(struct index_state *istate, { unsigned long consumed; + istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool)); if (istate->version == 4) { - mem_pool_init(&istate->ce_mem_pool, + mem_pool_init(istate->ce_mem_pool, estimate_cache_size_from_compressed(istate->cache_nr)); } else { - mem_pool_init(&istate->ce_mem_pool, + mem_pool_init(istate->ce_mem_pool, estimate_cache_size(mmap_size, istate->cache_nr)); } @@ -2070,7 +2073,8 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con if (istate->name_hash_initialized) BUG("the name hash isn't thread safe"); - mem_pool_init(&istate->ce_mem_pool, 0); + istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool)); + mem_pool_init(istate->ce_mem_pool, 0); /* ensure we have no more threads than we have blocks to process */ if (nr_threads > ieot->nr) @@ -2097,11 +2101,12 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con nr = 0; for (j = p->ieot_start; j < p->ieot_start + p->ieot_blocks; j++) nr += p->ieot->entries[j].nr; + istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool)); if (istate->version == 4) { - mem_pool_init(&p->ce_mem_pool, + mem_pool_init(p->ce_mem_pool, estimate_cache_size_from_compressed(nr)); } else { - mem_pool_init(&p->ce_mem_pool, + mem_pool_init(p->ce_mem_pool, estimate_cache_size(mmap_size, nr)); } @@ -2358,7 +2363,7 @@ int discard_index(struct index_state *istate) if (istate->ce_mem_pool) { mem_pool_discard(istate->ce_mem_pool, should_validate_cache_entries()); - istate->ce_mem_pool = NULL; + FREE_AND_NULL(istate->ce_mem_pool); } return 0; diff --git a/split-index.c b/split-index.c index e6154e4ea9..c0e8ad670d 100644 --- a/split-index.c +++ b/split-index.c @@ -79,8 +79,10 @@ void move_cache_to_base_index(struct index_state *istate) if (si->base && si->base->ce_mem_pool) { - if (!istate->ce_mem_pool) - mem_pool_init(&istate->ce_mem_pool, 0); + if (!istate->ce_mem_pool) { + istate->ce_mem_pool = xmalloc(sizeof(struct mem_pool)); + mem_pool_init(istate->ce_mem_pool, 0); + } mem_pool_combine(istate->ce_mem_pool, istate->split_index->base->ce_mem_pool); } -- gitgitgadget