linux-kernel - [PATCH v2 2/2] KVM: s390: pv: fix index value of replaced ASCE

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Date:   Wed,  5 Jul 2023 13:19:37 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        frankja@...ux.ibm.com, mhartmay@...ux.ibm.com, nsg@...ux.ibm.com,
        borntraeger@...ibm.com, nrb@...ux.ibm.com
Subject: [PATCH v2 2/2] KVM: s390: pv: fix index value of replaced ASCE

The index field of the struct page corresponding to a guest ASCE should
be 0. When replacing the ASCE in s390_replace_asce(), the index of the
new ASCE should also be set to 0.

Having the wrong index might lead to the wrong addresses being passed
around when notifying pte invalidations, and eventually to validity
intercepts (VM crash) if the prefix gets unmapped and the notifier gets
called with the wrong address.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 arch/s390/mm/gmap.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index f4b6fc746fce..7c77f246e101 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2853,6 +2853,7 @@ int s390_replace_asce(struct gmap *gmap)
 	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
 	if (!page)
 		return -ENOMEM;
+	page->index = 0;
 	table = page_to_virt(page);
 	memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));

-- 
2.41.0