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X-IronPort-AV: E=McAfee;i="6500,9779,10468"; a="285079350" X-IronPort-AV: E=Sophos;i="5.93,312,1654585200"; d="scan'208";a="285079350" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Sep 2022 23:54:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,312,1654585200"; d="scan'208";a="861440697" Received: from feng-clx.sh.intel.com ([10.238.200.228]) by fmsmga006.fm.intel.com with ESMTP; 12 Sep 2022 23:54:42 -0700 From: Feng Tang To: Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Dmitry Vyukov , Jonathan Corbet , Andrey Konovalov Cc: Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Feng Tang Subject: [PATCH v6 0/4] mm/slub: some debug enhancements for kmalloc Date: Tue, 13 Sep 2022 14:54:19 +0800 Message-Id: <20220913065423.520159-1-feng.tang@intel.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 ARC-Message-Signature: i=1; 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dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=JtHsBail; spf=pass (imf11.hostedemail.com: domain of feng.tang@intel.com designates 134.134.136.20 as permitted sender) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspamd-Server: rspam02 X-Stat-Signature: x3ns4qyac6zi5yagy84epfyr8wgq5wkf X-HE-Tag: 1663052087-997111 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: kmalloc's API family is critical for mm, and one of its nature is that it will round up the request size to a fixed one (mostly power of 2). When user requests memory for '2^n + 1' bytes, actually 2^(n+1) bytes could be allocated, so in worst case, there is around 50% memory space waste. The wastage is not a big issue for requests that get allocated/freed quickly, but may cause problems with objects that have longer life time, and there were some OOM cases in some extrem cases. This patchset(4/4) tries to : * Add a debug method to track each kmalloced object's wastage info, and show the call stack of original allocation (depends on SLAB_STORE_USER flag) (Patch 1) * Extend the redzone sanity check to the extra kmalloced buffer than requested, to better detect un-legitimate access to it. (depends on SLAB_STORE_USER & SLAB_RED_ZONE) (Patch 2/3/4, while 2/3 are preparation patches) The redzone part has been tested with code below: for (shift = 3; shift <= 12; shift++) { size = 1 << shift; buf = kmalloc(size + 4, GFP_KERNEL); /* We have 96, 196 kmalloc size, which is not power of 2 */ if (size == 64 || size == 128) oob_size = 16; else oob_size = size - 4; memset(buf + size + 4, 0xee, oob_size); kfree(buf); } Please help to review, thanks! - Feng --- Changelogs: since v5: * Refine code/comments and add more perf info in commit log for kzalloc change (Hyeonggoon Yoo) * change the kasan param name and refine comments about kasan+redzone handling (Andrey Konovalov) * put free pointer in meta data to make redzone check cover all kmalloc objects (Hyeonggoon Yoo) since v4: * fix a race issue in v3, by moving kmalloc debug init into alloc_debug_processing (Hyeonggon Yoo) * add 'partial_conext' for better parameter passing in get_partial() call chain (Vlastimil Babka) * update 'slub.rst' for 'alloc_traces' part (Hyeonggon Yoo) * update code comments for 'orig_size' since v3: * rebase against latest post 6.0-rc1 slab tree's 'for-next' branch * fix a bug reported by 0Day, that kmalloc-redzoned data and kasan's free meta data overlaps in the same kmalloc object data area since v2: * rebase against slab tree's 'for-next' branch * fix pointer handling (Kefeng Wang) * move kzalloc zeroing handling change to a separate patch (Vlastimil Babka) * make 'orig_size' only depend on KMALLOC & STORE_USER flag bits (Vlastimil Babka) since v1: * limit the 'orig_size' to kmalloc objects only, and save it after track in metadata (Vlastimil Babka) * fix a offset calculation problem in print_trailer since RFC: * fix problems in kmem_cache_alloc_bulk() and records sorting, improve the print format (Hyeonggon Yoo) * fix a compiling issue found by 0Day bot * update the commit log based info from iova developers Feng Tang (4): mm/slub: enable debugging memory wasting of kmalloc mm/slub: only zero the requested size of buffer for kzalloc mm: kasan: Add free_meta size info in struct kasan_cache mm/slub: extend redzone check to extra allocated kmalloc space than requested Documentation/mm/slub.rst | 33 +++--- include/linux/kasan.h | 2 + include/linux/slab.h | 2 + mm/kasan/common.c | 2 + mm/slab.c | 7 +- mm/slab.h | 9 +- mm/slab_common.c | 4 + mm/slub.c | 217 ++++++++++++++++++++++++++++++-------- 8 files changed, 214 insertions(+), 62 deletions(-) -- 2.34.1