From nobody Sun May 10 23:26:41 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6263CC433EF for ; Thu, 21 Apr 2022 12:53:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386002AbiDUM4V (ORCPT ); Thu, 21 Apr 2022 08:56:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385874AbiDUM4P (ORCPT ); Thu, 21 Apr 2022 08:56:15 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AA0432ED2 for ; Thu, 21 Apr 2022 05:53:25 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kkcph0gmDzFqW8; Thu, 21 Apr 2022 20:50:52 +0800 (CST) Received: from huawei.com (10.175.124.27) 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, 21 Apr 2022 20:53:23 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH v2 1/3] mm/swapfile: unuse_pte can map random data if swap read fails Date: Thu, 21 Apr 2022 20:53:46 +0800 Message-ID: <20220421125348.62483-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220421125348.62483-1-linmiaohe@huawei.com> References: <20220421125348.62483-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" There is a bug in unuse_pte(): when swap page happens to be unreadable, page filled with random data is mapped into user address space. In case of error, a special swap entry indicating swap read fails is set to the page table. So the swapcache page can be freed and the user won't end up with a permanently mounted swap because a sector is bad. And if the page is accessed later, the user process will be killed so that corrupted data is never consumed. On the other hand, if the page is never accessed, the user won't even notice it. Signed-off-by: Miaohe Lin Acked-by: David Hildenbrand --- include/linux/swap.h | 7 ++++++- include/linux/swapops.h | 10 ++++++++++ mm/memory.c | 5 ++++- mm/swapfile.c | 11 +++++++++++ 4 files changed, 31 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 5553189d0215..b82c196d8867 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -55,6 +55,10 @@ static inline int current_is_kswapd(void) * actions on faults. */ =20 +#define SWP_SWAPIN_ERROR_NUM 1 +#define SWP_SWAPIN_ERROR (MAX_SWAPFILES + SWP_HWPOISON_NUM + \ + SWP_MIGRATION_NUM + SWP_DEVICE_NUM + \ + SWP_PTE_MARKER_NUM) /* * PTE markers are used to persist information onto PTEs that are mapped w= ith * file-backed memories. As its name "PTE" hints, it should only be appli= ed to @@ -120,7 +124,8 @@ static inline int current_is_kswapd(void) =20 #define MAX_SWAPFILES \ ((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \ - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - SWP_PTE_MARKER_NUM) + SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - \ + SWP_PTE_MARKER_NUM - SWP_SWAPIN_ERROR_NUM) =20 /* * Magic header for a swap area. The first part of the union is diff --git a/include/linux/swapops.h b/include/linux/swapops.h index a291f210e7f8..9d989ed049a6 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -108,6 +108,16 @@ static inline void *swp_to_radix_entry(swp_entry_t ent= ry) return xa_mk_value(entry.val); } =20 +static inline swp_entry_t make_swapin_error_entry(struct page *page) +{ + return swp_entry(SWP_SWAPIN_ERROR, page_to_pfn(page)); +} + +static inline int is_swapin_error_entry(swp_entry_t entry) +{ + return swp_type(entry) =3D=3D SWP_SWAPIN_ERROR; +} + #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) static inline swp_entry_t make_readable_device_private_entry(pgoff_t offse= t) { diff --git a/mm/memory.c b/mm/memory.c index f4161fb07ffa..626f63858e0c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1488,7 +1488,8 @@ static unsigned long zap_pte_range(struct mmu_gather = *tlb, /* Only drop the uffd-wp marker if explicitly requested */ if (!zap_drop_file_uffd_wp(details)) continue; - } else if (is_hwpoison_entry(entry)) { + } else if (is_hwpoison_entry(entry) || + is_swapin_error_entry(entry)) { if (!should_zap_cows(details)) continue; } else { @@ -3728,6 +3729,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) ret =3D vmf->page->pgmap->ops->migrate_to_ram(vmf); } else if (is_hwpoison_entry(entry)) { ret =3D VM_FAULT_HWPOISON; + } else if (is_swapin_error_entry(entry)) { + ret =3D VM_FAULT_SIGBUS; } else if (is_pte_marker_entry(entry)) { ret =3D handle_pte_marker(vmf); } else { diff --git a/mm/swapfile.c b/mm/swapfile.c index 9398e915b36b..95b63f69f388 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1797,6 +1797,17 @@ static int unuse_pte(struct vm_area_struct *vma, pmd= _t *pmd, goto out; } =20 + if (unlikely(!PageUptodate(page))) { + pte_t pteval; + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + pteval =3D swp_entry_to_pte(make_swapin_error_entry(page)); + set_pte_at(vma->vm_mm, addr, pte, pteval); + swap_free(entry); + ret =3D 0; + goto out; + } + /* See do_swap_page() */ BUG_ON(!PageAnon(page) && PageMappedToDisk(page)); BUG_ON(PageAnon(page) && PageAnonExclusive(page)); --=20 2.23.0 From nobody Sun May 10 23:26:41 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12CDEC433F5 for ; Thu, 21 Apr 2022 12:53:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386094AbiDUM40 (ORCPT ); Thu, 21 Apr 2022 08:56:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385910AbiDUM4Q (ORCPT ); Thu, 21 Apr 2022 08:56:16 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 822FA32ECC for ; Thu, 21 Apr 2022 05:53:26 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KkcsQ6XwPzQn0n; Thu, 21 Apr 2022 20:53:14 +0800 (CST) Received: from huawei.com (10.175.124.27) 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, 21 Apr 2022 20:53:23 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH v2 2/3] mm/swapfile: Fix lost swap bits in unuse_pte() Date: Thu, 21 Apr 2022 20:53:47 +0800 Message-ID: <20220421125348.62483-3-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220421125348.62483-1-linmiaohe@huawei.com> References: <20220421125348.62483-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This is observed by code review only but not any real report. When we turn off swapping we could have lost the bits stored in the swap ptes. The new rmap-exclusive bit is fine since that turned into a page flag, but not for soft-dirty and uffd-wp. Add them. Suggested-by: Peter Xu Signed-off-by: Miaohe Lin --- mm/swapfile.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 95b63f69f388..332ccfc76142 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1783,7 +1783,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_= t *pmd, { struct page *swapcache; spinlock_t *ptl; - pte_t *pte; + pte_t *pte, new_pte; int ret =3D 1; =20 swapcache =3D page; @@ -1832,8 +1832,14 @@ static int unuse_pte(struct vm_area_struct *vma, pmd= _t *pmd, page_add_new_anon_rmap(page, vma, addr); lru_cache_add_inactive_or_unevictable(page, vma); } - set_pte_at(vma->vm_mm, addr, pte, - pte_mkold(mk_pte(page, vma->vm_page_prot))); + new_pte =3D pte_mkold(mk_pte(page, vma->vm_page_prot)); + if (pte_swp_soft_dirty(*pte)) + new_pte =3D pte_mksoft_dirty(new_pte); + if (pte_swp_uffd_wp(*pte)) { + new_pte =3D pte_mkuffd_wp(new_pte); + new_pte =3D pte_wrprotect(new_pte); + } + set_pte_at(vma->vm_mm, addr, pte, new_pte); swap_free(entry); out: pte_unmap_unlock(pte, ptl); --=20 2.23.0 From nobody Sun May 10 23:26:41 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57552C433EF for ; Thu, 21 Apr 2022 12:53:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386151AbiDUM41 (ORCPT ); Thu, 21 Apr 2022 08:56:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385925AbiDUM4Q (ORCPT ); Thu, 21 Apr 2022 08:56:16 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3743D32ED1 for ; Thu, 21 Apr 2022 05:53:27 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KkcsR4zytzhXqs; Thu, 21 Apr 2022 20:53:15 +0800 (CST) Received: from huawei.com (10.175.124.27) 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, 21 Apr 2022 20:53:24 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH v2 3/3] mm/madvise: free hwpoison and swapin error entry in madvise_free_pte_range Date: Thu, 21 Apr 2022 20:53:48 +0800 Message-ID: <20220421125348.62483-4-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220421125348.62483-1-linmiaohe@huawei.com> References: <20220421125348.62483-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Once the MADV_FREE operation has succeeded, callers can expect they might get zero-fill pages if accessing the memory again. Therefore it should be safe to delete the hwpoison entry and swapin error entry. There is no reason to kill the process if it has called MADV_FREE on the range. Suggested-by: Alistair Popple Signed-off-by: Miaohe Lin Acked-by: David Hildenbrand --- mm/madvise.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 4d6592488b51..5f4537511532 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -624,11 +624,14 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigne= d long addr, swp_entry_t entry; =20 entry =3D pte_to_swp_entry(ptent); - if (non_swap_entry(entry)) - continue; - nr_swap--; - free_swap_and_cache(entry); - pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); + if (!non_swap_entry(entry)) { + nr_swap--; + free_swap_and_cache(entry); + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); + } else if (is_hwpoison_entry(entry) || + is_swapin_error_entry(entry)) { + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); + } continue; } =20 --=20 2.23.0