linux-kernel - [PATCH] mm: stricter check on THP migration entry

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-next>] [day] [month] [year] [list]

Message-ID: <20220618073243.9423-1-linmiaohe@huawei.com>
Date:   Sat, 18 Jun 2022 15:32:43 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm: stricter check on THP migration entry

When VM_BUG_ON check for THP migration entry, the existing code only check
thp_migration_supported case, but not for !thp_migration_supported case.
If !thp_migration_supported() and !pmd_present(), the original code may
dead loop in theory.  To make the VM_BUG_ON check more consistent, we need
to catch both cases.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/memory.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index fee2884481f2..6a9a17c7f58a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5043,10 +5043,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
 
 		barrier();
 		if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
-			VM_BUG_ON(thp_migration_supported() &&
-					  !is_pmd_migration_entry(vmf.orig_pmd));
-			if (is_pmd_migration_entry(vmf.orig_pmd))
-				pmd_migration_entry_wait(mm, vmf.pmd);
+			VM_BUG_ON(!thp_migration_supported() ||
+				  !is_pmd_migration_entry(vmf.orig_pmd));
+			pmd_migration_entry_wait(mm, vmf.pmd);
 			return 0;
 		}
 		if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
-- 
2.23.0