linux-kernel - [PATCH 04/12] KVM: SEV: do not use list_replace

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: <20211123005036.2954379-5-pbonzini@redhat.com>
Date:   Mon, 22 Nov 2021 19:50:28 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pgonda@...gle.com
Subject: [PATCH 04/12] KVM: SEV: do not use list_replace_init on an empty list

list_replace_init cannot be used if the source is an empty list,
because "new->next->prev = new" will overwrite "old->next":

				new				old
				prev = new, next = new		prev = old, next = old
new->next = old->next		prev = new, next = old		prev = old, next = old
new->next->prev = new		prev = new, next = old		prev = old, next = new
new->prev = old->prev		prev = old, next = old		prev = old, next = old
new->next->prev = new		prev = old, next = old		prev = new, next = new

The desired outcome instead would be to leave both old and new the same
as they were (two empty circular lists).  Use list_cut_before, which
already has the necessary check and is documented to discard the
previous contents of the list that will hold the result.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/sev.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 21ac0a5de4e0..75955beb3770 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1613,8 +1613,7 @@ static void sev_migrate_from(struct kvm_sev_info *dst,
 	src->handle = 0;
 	src->pages_locked = 0;
 
-	INIT_LIST_HEAD(&dst->regions_list);
-	list_replace_init(&src->regions_list, &dst->regions_list);
+	list_cut_before(&dst->regions_list, &src->regions_list, &src->regions_list);
 }
 
 static int sev_es_migrate_from(struct kvm *dst, struct kvm *src)
-- 
2.27.0