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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 4006FC388F7 for ; Fri, 13 Nov 2020 07:03:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8C69C20B80 for ; Fri, 13 Nov 2020 07:03:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="vTA7EHji" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C69C20B80 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EA2846B0075; Fri, 13 Nov 2020 02:03:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E516B6B0078; Fri, 13 Nov 2020 02:03:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D1A7F6B007B; Fri, 13 Nov 2020 02:03:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0113.hostedemail.com [216.40.44.113]) by kanga.kvack.org (Postfix) with ESMTP id A47D66B0075 for ; Fri, 13 Nov 2020 02:03:46 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 4D2A0362A for ; Fri, 13 Nov 2020 07:03:46 +0000 (UTC) X-FDA: 77478504852.09.feast73_2717ab02730d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id 2F84E180AD801 for ; Fri, 13 Nov 2020 07:03:46 +0000 (UTC) X-HE-Tag: feast73_2717ab02730d X-Filterd-Recvd-Size: 13575 Received: from mail-qt1-f194.google.com (mail-qt1-f194.google.com [209.85.160.194]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Fri, 13 Nov 2020 07:03:45 +0000 (UTC) Received: by mail-qt1-f194.google.com with SMTP id p12so6066526qtp.7 for ; Thu, 12 Nov 2020 23:03:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2PkncTpQIdgHDydrhX/SeaNm5Vy35yKSw0V2poc3sOE=; b=vTA7EHjidIHa0QR6bMWC4IbyGdx/RH4kQZGkiBjdySaklqHjkVx3Pb9M6X5ypyZm1l TD83hfj3lNv1OiI0tRm3nVOFEt97ecxZFA6WH+lLxKtmI/DRVA71b6JrVVMsemNrWM30 rmexLos7IeBbt9tcvNXG3hwgp6YKMhsQ5tChI2MNMW476o/wdeYDqOChL6GMoYjwHUjt X+iTwV9m1Chlloj3gkDgi89WwhgQc0ttryexkfP1kePJroZXYZI6BFpiPSLZVw8M+PTF WIdZ2C7gjrElaWzKll9oDHHxtDcVo7urLHFLgfBaC4Fm8+DYSuhNUhz2aqQC050Pbnjb fCxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2PkncTpQIdgHDydrhX/SeaNm5Vy35yKSw0V2poc3sOE=; b=icAp6D5in3VtdIkoCO/oODgR+ulO8PA3ACE2ayT1oLhqUJ6C/P0aQpWH434Fadva9s Go5BBObOpeBgluLpkwUdxmnpconN49TcatQQq4LicArg3j3c2SMkgBUxKS/ufRuodrxu BzzRo7MEKplkS4EEiCvIPQ2uAEMCxgdgU5AUTETJayT3dE5WBozNVjOmUVfk7oJY9JKS 6SqftPtRhpXNU9OixCLd9KUlxf/E1NcvyXQZIkwGbo7oh2E+udmxIgUXf042h2HBzxgs JYRw1+IQMtGMOLSBvyprt7wkXqI/aLngDMHWaZioq3c8fV7Shy25xk4RLx3MO+HFpcD3 8zCg== X-Gm-Message-State: AOAM532C4iUWjqD0hyPGVjgeije/Ba/pXFv7Ibvk++oPXvlMEWb1HK+0 P/TzS4O1y+5S2Ns1pC379xDutUAngMrTn/T64L0vIg== X-Google-Smtp-Source: ABdhPJwZpia7Ugc2X36833y+Hf+b2aXwjH+F7F9ce4CNJ6t1/KP62DBdAXq0Ht4wwnYizYDiAlzaVNpvqDch8W1N7I8= X-Received: by 2002:ac8:1288:: with SMTP id y8mr763877qti.177.1605251024620; Thu, 12 Nov 2020 23:03:44 -0800 (PST) MIME-Version: 1.0 References: <1605162252-23886-1-git-send-email-Kuan-Ying.Lee@mediatek.com> <1605162252-23886-2-git-send-email-Kuan-Ying.Lee@mediatek.com> <1605234714.30076.18.camel@mtksdccf07> In-Reply-To: <1605234714.30076.18.camel@mtksdccf07> From: Dmitry Vyukov Date: Fri, 13 Nov 2020 08:03:32 +0100 Message-ID: Subject: Re: [PATCH 1/1] kasan: fix object remain in offline per-cpu quarantine To: Kuan-Ying Lee Cc: Andrey Ryabinin , Alexander Potapenko , Andrew Morton , Matthias Brugger , kasan-dev , Linux-MM , LKML , Linux ARM , linux-mediatek@lists.infradead.org, wsd_upstream , Miles Chen , nicholas.tang@mediatek.com Content-Type: text/plain; charset="UTF-8" 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 Fri, Nov 13, 2020 at 3:32 AM Kuan-Ying Lee wrote: > > On Thu, 2020-11-12 at 09:39 +0100, Dmitry Vyukov wrote: > > On Thu, Nov 12, 2020 at 7:25 AM Kuan-Ying Lee > > wrote: > > > > > > We hit this issue in our internal test. > > > When enabling generic kasan, a kfree()'d object is put into per-cpu > > > quarantine first. If the cpu goes offline, object still remains in > > > the per-cpu quarantine. If we call kmem_cache_destroy() now, slub > > > will report "Objects remaining" error. > > > > > > [ 74.982625] ============================================================================= > > > [ 74.983380] BUG test_module_slab (Not tainted): Objects remaining in test_module_slab on __kmem_cache_shutdown() > > > [ 74.984145] ----------------------------------------------------------------------------- > > > [ 74.984145] > > > [ 74.984883] Disabling lock debugging due to kernel taint > > > [ 74.985561] INFO: Slab 0x(____ptrval____) objects=34 used=1 fp=0x(____ptrval____) flags=0x2ffff00000010200 > > > [ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: G B 5.10.0-rc1-00007-g4525c8781ec0-dirty #10 > > > [ 74.987262] Hardware name: linux,dummy-virt (DT) > > > [ 74.987606] Call trace: > > > [ 74.987924] dump_backtrace+0x0/0x2b0 > > > [ 74.988296] show_stack+0x18/0x68 > > > [ 74.988698] dump_stack+0xfc/0x168 > > > [ 74.989030] slab_err+0xac/0xd4 > > > [ 74.989346] __kmem_cache_shutdown+0x1e4/0x3c8 > > > [ 74.989779] kmem_cache_destroy+0x68/0x130 > > > [ 74.990176] test_version_show+0x84/0xf0 > > > [ 74.990679] module_attr_show+0x40/0x60 > > > [ 74.991218] sysfs_kf_seq_show+0x128/0x1c0 > > > [ 74.991656] kernfs_seq_show+0xa0/0xb8 > > > [ 74.992059] seq_read+0x1f0/0x7e8 > > > [ 74.992415] kernfs_fop_read+0x70/0x338 > > > [ 74.993051] vfs_read+0xe4/0x250 > > > [ 74.993498] ksys_read+0xc8/0x180 > > > [ 74.993825] __arm64_sys_read+0x44/0x58 > > > [ 74.994203] el0_svc_common.constprop.0+0xac/0x228 > > > [ 74.994708] do_el0_svc+0x38/0xa0 > > > [ 74.995088] el0_sync_handler+0x170/0x178 > > > [ 74.995497] el0_sync+0x174/0x180 > > > [ 74.996050] INFO: Object 0x(____ptrval____) @offset=15848 > > > [ 74.996752] INFO: Allocated in test_version_show+0x98/0xf0 age=8188 cpu=6 pid=172 > > > [ 75.000802] stack_trace_save+0x9c/0xd0 > > > [ 75.002420] set_track+0x64/0xf0 > > > [ 75.002770] alloc_debug_processing+0x104/0x1a0 > > > [ 75.003171] ___slab_alloc+0x628/0x648 > > > [ 75.004213] __slab_alloc.isra.0+0x2c/0x58 > > > [ 75.004757] kmem_cache_alloc+0x560/0x588 > > > [ 75.005376] test_version_show+0x98/0xf0 > > > [ 75.005756] module_attr_show+0x40/0x60 > > > [ 75.007035] sysfs_kf_seq_show+0x128/0x1c0 > > > [ 75.007433] kernfs_seq_show+0xa0/0xb8 > > > [ 75.007800] seq_read+0x1f0/0x7e8 > > > [ 75.008128] kernfs_fop_read+0x70/0x338 > > > [ 75.008507] vfs_read+0xe4/0x250 > > > [ 75.008990] ksys_read+0xc8/0x180 > > > [ 75.009462] __arm64_sys_read+0x44/0x58 > > > [ 75.010085] el0_svc_common.constprop.0+0xac/0x228 > > > [ 75.011006] kmem_cache_destroy test_module_slab: Slab cache still has objects > > > > > > Register a cpu hotplug function to remove all objects in the offline > > > per-cpu quarantine when cpu is going offline. Set a per-cpu variable > > > to indicate this cpu is offline. > > > > > > Signed-off-by: Kuan-Ying Lee > > > --- > > > mm/kasan/quarantine.c | 59 +++++++++++++++++++++++++++++++++++++++++-- > > > 1 file changed, 57 insertions(+), 2 deletions(-) > > > > > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > > > index 4c5375810449..67fb91ae2bd0 100644 > > > --- a/mm/kasan/quarantine.c > > > +++ b/mm/kasan/quarantine.c > > > @@ -29,6 +29,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > #include "../slab.h" > > > #include "kasan.h" > > > @@ -97,6 +98,7 @@ static void qlist_move_all(struct qlist_head *from, struct qlist_head *to) > > > * guarded by quarantine_lock. > > > */ > > > > Hi Kuan-Ying, > > > > Thanks for fixing this. > > > > > static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); > > > +static DEFINE_PER_CPU(int, cpu_quarantine_offline); > > > > I think cpu_quarantine_offline is better be part of cpu_quarantine > > because it logically is and we already obtain a pointer to > > cpu_quarantine in quarantine_put, so it will also make the code a bit > > shorter. > > > > Ok. Got it. > > > > > > /* Round-robin FIFO array of batches. */ > > > static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; > > > @@ -176,6 +178,8 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) > > > unsigned long flags; > > > struct qlist_head *q; > > > struct qlist_head temp = QLIST_INIT; > > > + int *offline; > > > + struct qlist_head q_offline = QLIST_INIT; > > > > > > /* > > > * Note: irq must be disabled until after we move the batch to the > > > @@ -187,8 +191,16 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) > > > */ > > > local_irq_save(flags); > > > > > > - q = this_cpu_ptr(&cpu_quarantine); > > > - qlist_put(q, &info->quarantine_link, cache->size); > > > + offline = this_cpu_ptr(&cpu_quarantine_offline); > > > + if (*offline == 0) { > > > + q = this_cpu_ptr(&cpu_quarantine); > > > + qlist_put(q, &info->quarantine_link, cache->size); > > > + } else { > > > + qlist_put(&q_offline, &info->quarantine_link, cache->size); > > > + qlist_free_all(&q_offline, cache); > > > > This looks like a convoluted way to call qlink_free. I think it will > > be better to call qlink_free directly here. > > > > And why do we need this? Because CPU shutdown code can still free some > > objects afterwards? > > > > Yes, it is because IRQ can happen during CPU shutdown and free some > objects into offline CPU quarantine. > > > > + local_irq_restore(flags); > > > + return; > > > > You add both if/else and early return, this looks like unnecessary > > code complication. It would be simpler with: > > > > if (*offline) { > > qlink_free(...); > > return; > > } > > ... all current per-cpu local ... > > > > > > Thank you for reminder. v2 Will do it. > > > > + } > > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { > > > qlist_move_all(q, &temp); > > > > > > @@ -328,3 +340,46 @@ void quarantine_remove_cache(struct kmem_cache *cache) > > > > > > synchronize_srcu(&remove_cache_srcu); > > > } > > > + > > > +static int kasan_cpu_online(unsigned int cpu) > > > +{ > > > + int *offline; > > > + unsigned long flags; > > > + > > > + local_irq_save(flags); > > > > I assume this local_irq_save/restore is to prevent some warnings from > > this_cpu_ptr. > > But CPU online/offline callbacks should run without preemption already > > (preempting/rescheduling on other CPUs does not make sense for them, > > right?), so I would assume that is already at least preemption > > disabled or something. Is there this_cpu_ptr variant that won't > > produce warnings on its own in cpu online/offline callbacks? > > This whole function could be a 1-liner: > > this_cpu_ptr(&cpu_quarantine)->offline = true; > > So I am trying to understand if we could avoid all this unnecessary danse. > > > > Yes, it's unnecessary. v2 will fix it. > > > > > > + offline = this_cpu_ptr(&cpu_quarantine_offline); > > > + *offline = 0; > > > + local_irq_restore(flags); > > > + return 0; > > > +} > > > + > > > +static int kasan_cpu_offline(unsigned int cpu) > > > +{ > > > + struct kmem_cache *s; > > > + int *offline; > > > + unsigned long flags; > > > + > > > + local_irq_save(flags); > > > + offline = this_cpu_ptr(&cpu_quarantine_offline); > > > + *offline = 1; > > > + local_irq_restore(flags); > > > + > > > + mutex_lock(&slab_mutex); > > > + list_for_each_entry(s, &slab_caches, list) { > > > + per_cpu_remove_cache(s); > > > + } > > > + mutex_unlock(&slab_mutex); > > > > We just want to drop the whole per-cpu cache at once, right? I would > > assume there should be a simpler way to do this all at once, rather > > than doing this per-slab. > > > > Yes. > Is removing objects in per-cpu quarantine directly better? Yes, single qlist_free_all call looks much better than iteration over all slabs and removing in parts under the mutex. > struct qlist_head *q; > q = this_cpu_ptr(&cpu_quaratine); > q->offline = true; > qlist_free_all(q, NULL); > > > > + return 0; > > > +} > > > + > > > +static int __init kasan_cpu_offline_quarantine_init(void) > > > +{ > > > + int ret = 0; > > > + > > > + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online", > > > + kasan_cpu_online, kasan_cpu_offline); > > > + if (ret) > > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > > + return ret; > > > +} > > > +late_initcall(kasan_cpu_offline_quarantine_init); > > > -- > > > 2.18.0 > > > > > > -- > > > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > > > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605162252-23886-2-git-send-email-Kuan-Ying.Lee%40mediatek.com. > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605234714.30076.18.camel%40mtksdccf07.