linux-kernel - [PATCHv3 10/11] mm: Do not loose dirty and access bits in pmdp

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: <20170912153941.47012-11-kirill.shutemov@linux.intel.com>
Date:   Tue, 12 Sep 2017 18:39:40 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vineet Gupta <vgupta@...opsys.com>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Cc:     linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: [PATCHv3 10/11] mm: Do not loose dirty and access bits in pmdp_invalidate()

Vlastimil noted that pmdp_invalidate() is not atomic and we can loose
dirty and access bits if CPU sets them after pmdp dereference, but
before set_pmd_at().

The patch change pmdp_invalidate() to make the entry non-present atomically and
return previous value of the entry. This value can be used to check if
CPU set dirty/accessed bits under us.

The race window is very small and I haven't seen any reports that can be
attributed to the bug. For this reason, I don't think backporting to
stable trees needed.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reported-by: Vlastimil Babka <vbabka@...e.cz>
Cc: Hugh Dickins <hughd@...gle.com>
---
 include/asm-generic/pgtable.h | 2 +-
 mm/pgtable-generic.c          | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index bf0889eb774d..9df1da175fb0 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -324,7 +324,7 @@ static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma,
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
-extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 			    pmd_t *pmdp);
 #endif
 
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 1175f6a24fdb..3db8f2f76666 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -180,12 +180,12 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
-void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 		     pmd_t *pmdp)
 {
-	pmd_t entry = *pmdp;
-	set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry));
+	pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mknotpresent(*pmdp));
 	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+	return old;
 }
 #endif
 
-- 
2.14.1