From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753005AbbCXXJh (ORCPT ); Tue, 24 Mar 2015 19:09:37 -0400 Received: from mail-ie0-f170.google.com ([209.85.223.170]:35523 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751842AbbCXXJf (ORCPT ); Tue, 24 Mar 2015 19:09:35 -0400 Date: Tue, 24 Mar 2015 16:09:32 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Dave Kleikamp , Christoph Hellwig , Sebastian Ott , Mikulas Patocka , Catalin Marinas , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jfs-discussion@lists.sourceforge.net Subject: [patch v2 3/4] mm, mempool: poison elements backed by slab allocator In-Reply-To: Message-ID: References: User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mempools keep elements in a reserved pool for contexts in which allocation may not be possible. When an element is allocated from the reserved pool, its memory contents is the same as when it was added to the reserved pool. Because of this, elements lack any free poisoning to detect use-after-free errors. This patch adds free poisoning for elements backed by the slab allocator. This is possible because the mempool layer knows the object size of each element. When an element is added to the reserved pool, it is poisoned with POISON_FREE. When it is removed from the reserved pool, the contents are checked for POISON_FREE. If there is a mismatch, a warning is emitted to the kernel log. This is only effective for configs with CONFIG_DEBUG_SLAB or CONFIG_SLUB_DEBUG_ON. Signed-off-by: David Rientjes --- v2: switch dependency to CONFIG_DEBUG_SLAB or CONFIG_SLUB_DEBUG_ON mm/mempool.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 63 insertions(+), 2 deletions(-) diff --git a/mm/mempool.c b/mm/mempool.c --- a/mm/mempool.c +++ b/mm/mempool.c @@ -17,16 +17,77 @@ #include #include "slab.h" +#if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON) +static void poison_error(mempool_t *pool, void *element, size_t size, + size_t byte) +{ + const int nr = pool->curr_nr; + const int start = max_t(int, byte - (BITS_PER_LONG / 8), 0); + const int end = min_t(int, byte + (BITS_PER_LONG / 8), size); + int i; + + pr_err("BUG: mempool element poison mismatch\n"); + pr_err("Mempool %p size %ld\n", pool, size); + pr_err(" nr=%d @ %p: %s0x", nr, element, start > 0 ? "... " : ""); + for (i = start; i < end; i++) + pr_cont("%x ", *(u8 *)(element + i)); + pr_cont("%s\n", end < size ? "..." : ""); + dump_stack(); +} + +static void check_slab_element(mempool_t *pool, void *element) +{ + if (pool->free == mempool_free_slab || pool->free == mempool_kfree) { + size_t size = ksize(element); + u8 *obj = element; + size_t i; + + for (i = 0; i < size; i++) { + u8 exp = (i < size - 1) ? POISON_FREE : POISON_END; + + if (obj[i] != exp) { + poison_error(pool, element, size, i); + return; + } + } + memset(obj, POISON_INUSE, size); + } +} + +static void poison_slab_element(mempool_t *pool, void *element) +{ + if (pool->alloc == mempool_alloc_slab || + pool->alloc == mempool_kmalloc) { + size_t size = ksize(element); + u8 *obj = element; + + memset(obj, POISON_FREE, size - 1); + obj[size - 1] = POISON_END; + } +} +#else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */ +static inline void check_slab_element(mempool_t *pool, void *element) +{ +} +static inline void poison_slab_element(mempool_t *pool, void *element) +{ +} +#endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */ + static void add_element(mempool_t *pool, void *element) { BUG_ON(pool->curr_nr >= pool->min_nr); + poison_slab_element(pool, element); pool->elements[pool->curr_nr++] = element; } static void *remove_element(mempool_t *pool) { - BUG_ON(pool->curr_nr <= 0); - return pool->elements[--pool->curr_nr]; + void *element = pool->elements[--pool->curr_nr]; + + BUG_ON(pool->curr_nr < 0); + check_slab_element(pool, element); + return element; } /**