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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3600EC43334 for ; Wed, 13 Jul 2022 12:10:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A065B94012C; Wed, 13 Jul 2022 08:10:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B6D29400E5; Wed, 13 Jul 2022 08:10:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D66B94012C; Wed, 13 Jul 2022 08:10:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 7EA699400E5 for ; Wed, 13 Jul 2022 08:10:23 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 5422F1206E9 for ; Wed, 13 Jul 2022 12:10:23 +0000 (UTC) X-FDA: 79681959126.04.2E18B3A Received: from out30-57.freemail.mail.aliyun.com (out30-57.freemail.mail.aliyun.com [115.124.30.57]) by imf07.hostedemail.com (Postfix) with ESMTP id 5C41840042 for ; Wed, 13 Jul 2022 12:10:19 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=rongwei.wang@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0VJDq.BW_1657714212; Received: from 30.240.98.52(mailfrom:rongwei.wang@linux.alibaba.com fp:SMTPD_---0VJDq.BW_1657714212) by smtp.aliyun-inc.com; Wed, 13 Jul 2022 20:10:14 +0800 Message-ID: Date: Wed, 13 Jul 2022 20:10:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:103.0) Gecko/20100101 Thunderbird/103.0 Subject: Re: [PATCH v2 1/3] mm/slub: fix the race between validate_slab and slab_free Content-Language: en-US To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, iamjoonsoo.kim@lge.com, rientjes@google.com, penberg@kernel.org, cl@gentwo.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Feng Tang References: <20220712022807.44113-1-rongwei.wang@linux.alibaba.com> From: Rongwei Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf07.hostedemail.com: domain of rongwei.wang@linux.alibaba.com designates 115.124.30.57 as permitted sender) smtp.mailfrom=rongwei.wang@linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657714222; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=objdWpBsyRrnX+eEccVbX5X81V+EdS8zOR3h/DiiY+I=; b=kjxaRFA+3EtfGH+FE2d+CSOqHqU/4N0N0fCSZZNMv+VM1bdD4cAnppLscrzuk6MQEJA6GT IfspHoKbLxrgrKRzVJ0+kFzDfdFw5SShtjpI0l+WtOZ8G2VcecjWMYc6A/hNGXqSwQdUdi /bWCw4Ga3TpQIzNdXauHC9dPhAb+fag= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657714222; a=rsa-sha256; cv=none; b=YzP5voAlgyP/br9gPAq3qjCFcDd44C6iz35zqgqEpo1jm+fQxBpYXz2lsWYqD/VVpbOEGN RxZjYX4mIVbumkDkLZKq9mKHoR0U7cY6tONnyHnnur6tRWSc3EgpEhlWC+I0pHfXy0Xt7H GNm0FCSK8NgD5jaF9gUTjIV8/Sn7Wek= X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5C41840042 X-Stat-Signature: atjm5yie7oudfncudgux7wa7g8ryzjxa Authentication-Results: imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf07.hostedemail.com: domain of rongwei.wang@linux.alibaba.com designates 115.124.30.57 as permitted sender) smtp.mailfrom=rongwei.wang@linux.alibaba.com X-Rspam-User: X-HE-Tag: 1657714219-784441 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: On 7/13/22 6:22 PM, Hyeonggon Yoo wrote: > On Tue, Jul 12, 2022 at 10:28:05AM +0800, Rongwei Wang wrote: >> In use cases where allocating and freeing slab frequently, some >> error messages, such as "Left Redzone overwritten", "First byte >> 0xbb instead of 0xcc" would be printed when validating slabs. >> That's because an object has been filled with SLAB_RED_INACTIVE, >> but has not been added to slab's freelist. And between these >> two states, the behaviour of validating slab is likely to occur. >> >> Actually, it doesn't mean the slab can not work stably. But, these >> confusing messages will disturb slab debugging more or less. >> >> Signed-off-by: Rongwei Wang >> --- >> mm/slub.c | 43 +++++++++++++++++++++++++------------------ >> 1 file changed, 25 insertions(+), 18 deletions(-) >> > > This makes the code more complex. > > A part of me says it may be more pleasant to split implementation > allocating from caches for debugging. That would make it simpler. > > something like: > > __slab_alloc() { > if (kmem_cache_debug(s)) > slab_alloc_debug() > else > ___slab_alloc() > } > > slab_free() { > if (kmem_cache_debug(s)) > slab_free_debug() > else > __do_slab_free() > } Oh, I also have same idea, but not sure whether it is accepted because of it needs more changes than now. Since you agree with this way, I can rewrite this code. Thanks. > > See also: > https://lore.kernel.org/lkml/faf416b9-f46c-8534-7fb7-557c046a564d@suse.cz/ Thanks, it seems that I had missed it. > >> diff --git a/mm/slub.c b/mm/slub.c >> index b1281b8654bd..e950d8df8380 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -1391,18 +1391,16 @@ static noinline int free_debug_processing( >> void *head, void *tail, int bulk_cnt, >> unsigned long addr) >> { >> - struct kmem_cache_node *n = get_node(s, slab_nid(slab)); >> void *object = head; >> int cnt = 0; >> - unsigned long flags, flags2; >> + unsigned long flags; >> int ret = 0; >> depot_stack_handle_t handle = 0; >> >> if (s->flags & SLAB_STORE_USER) >> handle = set_track_prepare(); >> >> - spin_lock_irqsave(&n->list_lock, flags); >> - slab_lock(slab, &flags2); >> + slab_lock(slab, &flags); >> >> if (s->flags & SLAB_CONSISTENCY_CHECKS) { >> if (!check_slab(s, slab)) >> @@ -1435,8 +1433,7 @@ static noinline int free_debug_processing( >> slab_err(s, slab, "Bulk freelist count(%d) invalid(%d)\n", >> bulk_cnt, cnt); >> >> - slab_unlock(slab, &flags2); >> - spin_unlock_irqrestore(&n->list_lock, flags); >> + slab_unlock(slab, &flags); >> if (!ret) >> slab_fix(s, "Object at 0x%p not freed", object); >> return ret; >> @@ -3330,7 +3327,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, >> >> { >> void *prior; >> - int was_frozen; >> + int was_frozen, to_take_off = 0; >> struct slab new; >> unsigned long counters; >> struct kmem_cache_node *n = NULL; >> @@ -3341,14 +3338,23 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, >> if (kfence_free(head)) >> return; >> >> - if (kmem_cache_debug(s) && >> - !free_debug_processing(s, slab, head, tail, cnt, addr)) >> - return; >> + n = get_node(s, slab_nid(slab)); >> + if (kmem_cache_debug(s)) { >> + int ret; >> >> - do { >> - if (unlikely(n)) { >> + spin_lock_irqsave(&n->list_lock, flags); >> + ret = free_debug_processing(s, slab, head, tail, cnt, addr); >> + if (!ret) { >> spin_unlock_irqrestore(&n->list_lock, flags); >> - n = NULL; >> + return; >> + } >> + } >> + >> + do { >> + if (unlikely(to_take_off)) { >> + if (!kmem_cache_debug(s)) >> + spin_unlock_irqrestore(&n->list_lock, flags); >> + to_take_off = 0; >> } >> prior = slab->freelist; >> counters = slab->counters; >> @@ -3369,8 +3375,6 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, >> new.frozen = 1; >> >> } else { /* Needs to be taken off a list */ >> - >> - n = get_node(s, slab_nid(slab)); >> /* >> * Speculatively acquire the list_lock. >> * If the cmpxchg does not succeed then we may >> @@ -3379,8 +3383,10 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, >> * Otherwise the list_lock will synchronize with >> * other processors updating the list of slabs. >> */ >> - spin_lock_irqsave(&n->list_lock, flags); >> + if (!kmem_cache_debug(s)) >> + spin_lock_irqsave(&n->list_lock, flags); >> >> + to_take_off = 1; >> } >> } >> >> @@ -3389,8 +3395,9 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, >> head, new.counters, >> "__slab_free")); >> >> - if (likely(!n)) { >> - >> + if (likely(!to_take_off)) { >> + if (kmem_cache_debug(s)) >> + spin_unlock_irqrestore(&n->list_lock, flags); >> if (likely(was_frozen)) { >> /* >> * The list lock was not taken therefore no list >> -- >> 2.27.0 >>