linux-kernel - [RFCv2 10/13] mm: Keep page reference for hwpoison entries

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210416154106.23721-11-kirill.shutemov@linux.intel.com>
Date:   Fri, 16 Apr 2021 18:41:03 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     David Rientjes <rientjes@...gle.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Peter Gonda <pgonda@...gle.com>,
        David Hildenbrand <david@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFCv2 10/13] mm: Keep page reference for hwpoison entries

On migration we drop referece to a page once PTE gets replaced with a
migration entry. Migration code keeps the last reference on the page
that gets dropped once migration is complete.

We do the same for hwpoison entries, but it doesn't work: nobody keeps
the reference once page is remapped with hwpoison entries.

Keep page referenced on setting up hwpoison entries, copy the reference
on fork() and return on zap().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/memory.c | 6 ++++++
 mm/rmap.c   | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index feff48e1465a..b15b0c582186 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -767,6 +767,9 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 				pte = pte_swp_mkuffd_wp(pte);
 			set_pte_at(src_mm, addr, src_pte, pte);
 		}
+	} else if (is_hwpoison_entry(entry)) {
+		page = hwpoison_entry_to_page(entry);
+		get_page(page);
 	}
 	set_pte_at(dst_mm, addr, dst_pte, pte);
 	return 0;
@@ -1305,6 +1308,9 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 
 			page = migration_entry_to_page(entry);
 			rss[mm_counter(page)]--;
+
+		} else if (is_hwpoison_entry(entry)) {
+			put_page(hwpoison_entry_to_page(entry));
 		}
 		if (unlikely(!free_swap_and_cache(entry)))
 			print_bad_pte(vma, addr, ptent, NULL);
diff --git a/mm/rmap.c b/mm/rmap.c
index 08c56aaf72eb..f08d1fc28522 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1575,7 +1575,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 				dec_mm_counter(mm, mm_counter(page));
 				set_pte_at(mm, address, pvmw.pte, pteval);
 			}
-
+			get_page(page);
 		} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
 			/*
 			 * The guest indicated that the page content is of no
-- 
2.26.3