From: Claudio Imbrenda <imbrenda@linux.ibm.com>
Date: Fri, 6 Feb 2026 14:35:52 +0000 (+0100)
Subject: KVM: s390: vsie: Fix race in walk_guest_tables()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b6ab71a27c50942cfc10d12ca3f3c0cfb1634d19;p=thirdparty%2Fkernel%2Fstable.git

KVM: s390: vsie: Fix race in walk_guest_tables()

It is possible that walk_guest_tables() is called on a shadow gmap that
has been removed already, in which case its parent will be NULL.

In such case, return -EAGAIN and let the callers deal with it.

Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 67de47a81a87..4630b2a067ea 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1287,7 +1287,10 @@ static int walk_guest_tables(struct gmap *sg, unsigned long saddr, struct pgtwal
 	union asce asce;
 	int rc;
 
+	if (!parent)
+		return -EAGAIN;
 	kvm = parent->kvm;
+	WARN_ON(!kvm);
 	asce = sg->guest_asce;
 	entries = get_entries(w);