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 48430C433F5 for ; Thu, 7 Apr 2022 13:38:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8C76E6B0072; Thu, 7 Apr 2022 09:38:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 877166B0073; Thu, 7 Apr 2022 09:38:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 718888D0001; Thu, 7 Apr 2022 09:38:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 6473E6B0072 for ; Thu, 7 Apr 2022 09:38:42 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 31F971246C6 for ; Thu, 7 Apr 2022 13:38:32 +0000 (UTC) X-FDA: 79330187664.11.F688EDA Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf04.hostedemail.com (Postfix) with ESMTP id DFA2E40004 for ; Thu, 7 Apr 2022 13:38:30 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KZ2V25yXBzXdYY; Thu, 7 Apr 2022 21:36:42 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 7 Apr 2022 21:38:27 +0800 Subject: Re: [PATCH v7] mm/hwpoison: fix race between hugetlb free/demotion and memory_failure_hugetlb() To: Naoya Horiguchi CC: Andrew Morton , Mike Kravetz , Yang Shi , Dan Carpenter , Naoya Horiguchi , , Linux-MM References: <20220407112929.1344748-1-naoya.horiguchi@linux.dev> From: Miaohe Lin Message-ID: <4b5ad6c3-99a0-b04f-21ad-8ade46984c76@huawei.com> Date: Thu, 7 Apr 2022 21:38:26 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220407112929.1344748-1-naoya.horiguchi@linux.dev> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: Authentication-Results: imf04.hostedemail.com; dkim=none; spf=pass (imf04.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DFA2E40004 X-Stat-Signature: e8azmujegfe6bqh64dz6x1ukmf98te5f X-HE-Tag: 1649338710-423655 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 2022/4/7 19:29, Naoya Horiguchi wrote: > From: Naoya Horiguchi > > There is a race condition between memory_failure_hugetlb() and hugetlb > free/demotion, which causes setting PageHWPoison flag on the wrong page. > The one simple result is that wrong processes can be killed, but another > (more serious) one is that the actual error is left unhandled, so no one > prevents later access to it, and that might lead to more serious results > like consuming corrupted data. > > Think about the below race window: > > CPU 1 CPU 2 > memory_failure_hugetlb > struct page *head = compound_head(p); > hugetlb page might be freed to > buddy, or even changed to another > compound page. > > get_hwpoison_page -- page is not what we want now... > > The current code first does prechecks roughly and then reconfirms > after taking refcount, but it's found that it makes code overly > complicated, so move the prechecks in a single hugetlb_lock range. > > A newly introduced function, try_memory_failure_hugetlb(), always > takes hugetlb_lock (even for non-hugetlb pages). That can be > improved, but memory_failure() is rare in principle, so should > not be a big problem. > > Fixes: 761ad8d7c7b5 ("mm: hwpoison: introduce memory_failure_hugetlb()") > Reported-by: Mike Kravetz > Signed-off-by: Naoya Horiguchi > Cc: stable@vger.kernel.org > --- > ChangeLog v6 -> v7: > - Move lock_page() to try_memory_failure_hugetlb() > (based on bug report from Dan Carpenter) > - Add Fixes: tag and CC to stable. > > ChangeLog v5 -> v6: > - Moved racy precheck operations into hugetlb_lock (based on > Mike's comment). > - rebased onto v5.18-rc1. > - dropped CC to stable. > > ChangeLog v4 -> v5: > - call TestSetPageHWPoison() when page_handle_poison() fails. > - call TestSetPageHWPoison() for unhandlable cases (MF_MSG_UNKNOWN and > MF_MSG_DIFFERENT_PAGE_SIZE). > - Set PageHWPoison on the head page only when the error page is surely > a hugepage, otherwise set the flag on the raw page. > - rebased onto v5.17-rc8-mmotm-2022-03-16-17-42 > > ChangeLog v3 -> v4: > - squash with "mm/memory-failure.c: fix race with changing page > compound again". > - update patch subject and description based on it. > > ChangeLog v2 -> v3: > - rename the patch because page lock is not the primary factor to > solve the reported issue. > - updated description in the same manner. > - call page_handle_poison() instead of __page_handle_poison() for > free hugepage case. > - reorder put_page and unlock_page (thanks to Miaohe Lin) > > ChangeLog v1 -> v2: > - pass subpage to get_hwpoison_huge_page() instead of head page. > - call compound_head() in hugetlb_lock to avoid race with hugetlb > demotion/free. > --- > include/linux/hugetlb.h | 6 ++ > include/linux/mm.h | 8 +++ > mm/hugetlb.c | 10 +++ > mm/memory-failure.c | 142 +++++++++++++++++++++++++++++----------- > 4 files changed, 126 insertions(+), 40 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 53c1b6082a4c..ac2a1d758a80 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -169,6 +169,7 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end, > long freed); > bool isolate_huge_page(struct page *page, struct list_head *list); > int get_hwpoison_huge_page(struct page *page, bool *hugetlb); > +int get_huge_page_for_hwpoison(unsigned long pfn, int flags); > void putback_active_hugepage(struct page *page); > void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason); > void free_huge_page(struct page *page); > @@ -378,6 +379,11 @@ static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb) > return 0; > } > > +static inline int get_huge_page_for_hwpoison(unsigned long pfn, int flags) > +{ > + return 0; > +} > + > static inline void putback_active_hugepage(struct page *page) > { > } > diff --git a/include/linux/mm.h b/include/linux/mm.h > index e34edb775334..9f44254af8ce 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3197,6 +3197,14 @@ extern int sysctl_memory_failure_recovery; > extern void shake_page(struct page *p); > extern atomic_long_t num_poisoned_pages __read_mostly; > extern int soft_offline_page(unsigned long pfn, int flags); > +#ifdef CONFIG_MEMORY_FAILURE > +extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags); > +#else > +static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags) > +{ > + return 0; > +} > +#endif > > #ifndef arch_memory_failure > static inline int arch_memory_failure(unsigned long pfn, int flags) > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index b34f50156f7e..c4f19e1a0807 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6782,6 +6782,16 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb) > return ret; > } > > +int get_huge_page_for_hwpoison(unsigned long pfn, int flags) > +{ > + int ret; > + > + spin_lock_irq(&hugetlb_lock); > + ret = __get_huge_page_for_hwpoison(pfn, flags); > + spin_unlock_irq(&hugetlb_lock); > + return ret; > +} > + > void putback_active_hugepage(struct page *page) > { > spin_lock_irq(&hugetlb_lock); > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index dcb6bb9cf731..3606800d3488 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1498,48 +1498,112 @@ static int try_to_split_thp_page(struct page *page, const char *msg) > return 0; > } > > -static int memory_failure_hugetlb(unsigned long pfn, int flags) > +/* > + * Called from hugetlb code with hugetlb_lock held. > + * > + * Return values: > + * 0 - free hugepage > + * 1 - in-use hugepage > + * 2 - not a hugepage > + * -EBUSY - the hugepage is busy (try to retry) > + * -EOPNOTSUPP - error handling is cancelled due to hwpoison_filter() > + * -EHWPOISON - the hugepage is already hwpoisoned > + */ > +int __get_huge_page_for_hwpoison(unsigned long pfn, int flags) > +{ > + struct page *page = pfn_to_page(pfn); > + struct page *head = compound_head(page); > + int ret = 2; /* fallback to normal page handling */ > + bool count_increased = false; > + > + if (!PageHeadHuge(head)) > + goto out; > + > + if (flags & MF_COUNT_INCREASED) { > + ret = 1; > + count_increased = true; > + } else if (HPageFreed(head) || HPageMigratable(head)) { > + ret = get_page_unless_zero(head); > + if (ret) > + count_increased = true; > + } else { > + ret = -EBUSY; > + goto out; > + } > + > + if (hwpoison_filter(page)) { > + ret = -EOPNOTSUPP; > + goto out; > + } Now hwpoison_filter is done without lock_page + unlock_page. Is this ok or lock_page + unlock_page pair is indeed required? > + > + if (TestSetPageHWPoison(head)) { > + ret = -EHWPOISON; > + goto out; > + } Without this patch, page refcnt is not decremented if MF_COUNT_INCREASED is set in flags when PageHWPoison is already set. So I think this patch also fixes that issue. Thanks! > + > + return ret; > +out: > + if (count_increased) > + put_page(head); > + return ret; > +} > + > +#ifdef CONFIG_HUGETLB_PAGE > +/* > + * Taking refcount of hugetlb pages needs extra care about race conditions > + * with basic operations like hugepage allocation/free/demotion. > + * So all necessary prechecks for hwpoison (like pinning, testing/setting > + * PageHWPoison, and hwpoison_filter) are done in single hugetlb_lock range. > + */ > +static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) > { > - struct page *p = pfn_to_page(pfn); > - struct page *head = compound_head(p); > int res; > + struct page *p = pfn_to_page(pfn); > + struct page *head; > unsigned long page_flags; > + bool retry = true; > > - if (TestSetPageHWPoison(head)) { > - pr_err("Memory failure: %#lx: already hardware poisoned\n", > - pfn); > - res = -EHWPOISON; > - if (flags & MF_ACTION_REQUIRED) > + *hugetlb = 1; > +retry: > + res = get_huge_page_for_hwpoison(pfn, flags); > + if (res == 2) { /* fallback to normal page handling */ > + *hugetlb = 0; > + return 0; > + } else if (res == -EOPNOTSUPP) { > + return res; > + } else if (res == -EHWPOISON) { > + pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn); > + if (flags & MF_ACTION_REQUIRED) { > + head = compound_head(p); > res = kill_accessing_process(current, page_to_pfn(head), flags); > + } > + return res; > + } else if (res == -EBUSY) { > + if (retry) { > + retry = false; > + goto retry; > + } > + action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); > return res; > } > > num_poisoned_pages_inc(); > > - if (!(flags & MF_COUNT_INCREASED)) { > - res = get_hwpoison_page(p, flags); > - if (!res) { > - lock_page(head); > - if (hwpoison_filter(p)) { > - if (TestClearPageHWPoison(head)) > - num_poisoned_pages_dec(); > - unlock_page(head); > - return -EOPNOTSUPP; > - } > - unlock_page(head); > - res = MF_FAILED; > - if (__page_handle_poison(p)) { > - page_ref_inc(p); > - res = MF_RECOVERED; > - } > - action_result(pfn, MF_MSG_FREE_HUGE, res); > - return res == MF_RECOVERED ? 0 : -EBUSY; > - } else if (res < 0) { > - action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); > - return -EBUSY; > + /* > + * Handling free hugepage. The possible race with hugepage allocation > + * or demotion can be prevented by PageHWPoison flag. > + */ > + if (res == 0) { > + res = MF_FAILED; > + if (__page_handle_poison(p)) { > + page_ref_inc(p); > + res = MF_RECOVERED; > } > + action_result(pfn, MF_MSG_FREE_HUGE, res); > + return res == MF_RECOVERED ? 0 : -EBUSY; > } > > + head = compound_head(p); > lock_page(head); > > /* IMHO, the below code could be removed now as we fetch the refcnt under the hugetlb_lock: /* * The page could have changed compound pages due to race window. * If this happens just bail out. */ if (!PageHuge(p) || compound_head(p) != head) { action_result(pfn, MF_MSG_DIFFERENT_PAGE_SIZE, MF_IGNORED); res = -EBUSY; goto out; } But this might be another patch. Many thanks for your hard work! :) > @@ -1554,14 +1618,6 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) > > page_flags = head->flags; > > - if (hwpoison_filter(p)) { > - if (TestClearPageHWPoison(head)) > - num_poisoned_pages_dec(); > - put_page(p); > - res = -EOPNOTSUPP; > - goto out; > - } > - > /* > * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so > * simply disable it. In order to make it work properly, we need > @@ -1588,6 +1644,12 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) > unlock_page(head); > return res; > } > +#else > +static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) > +{ > + return 0; > +} > +#endif > > static int memory_failure_dev_pagemap(unsigned long pfn, int flags, > struct dev_pagemap *pgmap) > @@ -1712,6 +1774,7 @@ int memory_failure(unsigned long pfn, int flags) > int res = 0; > unsigned long page_flags; > bool retry = true; > + int hugetlb = 0; > > if (!sysctl_memory_failure_recovery) > panic("Memory failure on page %lx", pfn); > @@ -1739,10 +1802,9 @@ int memory_failure(unsigned long pfn, int flags) > } > > try_again: > - if (PageHuge(p)) { > - res = memory_failure_hugetlb(pfn, flags); > + res = try_memory_failure_hugetlb(pfn, flags, &hugetlb); > + if (hugetlb) > goto unlock_mutex; > - } > > if (TestSetPageHWPoison(p)) { > pr_err("Memory failure: %#lx: already hardware poisoned\n", >