[PATCH v4 02/13] KVM: s390: Fix leaking of PGM_ADDRESSING to userspace
From: Claudio Imbrenda
Date: Tue Jul 28 2026 - 13:26:41 EST
If kvm_s390_set_cmma_bits() is asked to set CMMA values outside of a
memslot, PGM_ADDRESSING (5) is returned, instead of a negative error
value.
Same issue with kvm_s390_{g,s}et_skeys(), kvm_s390_keyop(), and
dat_reset_reference_bit().
Fix by returning -EFAULT whenever the return value would be > 0, which
is consistent with the behaviour before the gmap rewrite.
Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
arch/s390/kvm/dat.c | 16 ++++++++++------
arch/s390/kvm/dat.h | 2 +-
arch/s390/kvm/kvm-s390.c | 16 ++++++++--------
arch/s390/kvm/priv.c | 5 +++--
4 files changed, 22 insertions(+), 17 deletions(-)
diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
index ed4259d17629..171b61959908 100644
--- a/arch/s390/kvm/dat.c
+++ b/arch/s390/kvm/dat.c
@@ -755,13 +755,15 @@ int dat_cond_set_storage_key(struct kvm_s390_mmu_cache *mmc, union asce asce, gf
return rc;
}
-int dat_reset_reference_bit(union asce asce, gfn_t gfn)
+int dat_reset_reference_bit(union asce asce, gfn_t gfn, union skey *skey)
{
union pgste pgste, old;
union crste *crstep;
union pte *ptep;
int rc;
+ skey->skey = 0;
+
rc = dat_entry_walk(NULL, gfn, asce, DAT_WALK_ANY, TABLE_TYPE_PAGE_TABLE, &crstep, &ptep);
if (rc)
return rc;
@@ -771,21 +773,23 @@ int dat_reset_reference_bit(union asce asce, gfn_t gfn)
if (!crste.h.fc || !crste.s.fc1.pr)
return 0;
- return page_reset_referenced(large_crste_to_phys(*crstep, gfn));
+ skey->skey = page_reset_referenced(large_crste_to_phys(*crstep, gfn)) << 1;
+ return 0;
}
old = pgste_get_lock(ptep);
pgste = old;
if (!ptep->h.i) {
- rc = page_reset_referenced(pte_origin(*ptep));
- pgste.hr = rc >> 1;
+ skey->skey = page_reset_referenced(pte_origin(*ptep)) << 1;
+ pgste.hr = skey->r;
}
- rc |= (pgste.gr << 1) | pgste.gc;
+ skey->r |= pgste.gr;
+ skey->c |= pgste.gc;
pgste.gr = 0;
dat_update_ptep_sd(old, pgste, ptep);
pgste_set_unlock(ptep, pgste);
- return rc;
+ return 0;
}
static long dat_reset_skeys_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h
index fad605305e05..141ee7b9f019 100644
--- a/arch/s390/kvm/dat.h
+++ b/arch/s390/kvm/dat.h
@@ -537,7 +537,7 @@ int dat_set_storage_key(struct kvm_s390_mmu_cache *mc, union asce asce, gfn_t gf
union skey skey, bool nq);
int dat_cond_set_storage_key(struct kvm_s390_mmu_cache *mmc, union asce asce, gfn_t gfn,
union skey skey, union skey *oldkey, bool nq, bool mr, bool mc);
-int dat_reset_reference_bit(union asce asce, gfn_t gfn);
+int dat_reset_reference_bit(union asce asce, gfn_t gfn, union skey *skey);
long dat_reset_skeys(union asce asce, gfn_t start);
unsigned long dat_get_ptval(struct page_table *table, struct ptval_param param);
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f86b4b0b356f..7bc6426f5f4d 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -571,7 +571,7 @@ static int kvm_s390_keyop(struct kvm_s390_mmu_cache *mc, struct kvm *kvm, int op
switch (op) {
case KVM_S390_KEYOP_SSKE:
r = dat_cond_set_storage_key(mc, asce, gfn, skey, &skey, 0, 0, 0);
- if (r >= 0)
+ if (r == 0 || r == 1)
return skey.skey;
break;
case KVM_S390_KEYOP_ISKE:
@@ -580,14 +580,14 @@ static int kvm_s390_keyop(struct kvm_s390_mmu_cache *mc, struct kvm *kvm, int op
return skey.skey;
break;
case KVM_S390_KEYOP_RRBE:
- r = dat_reset_reference_bit(asce, gfn);
- if (r > 0)
- return r << 1;
+ r = dat_reset_reference_bit(asce, gfn, &skey);
+ if (!r)
+ return skey.skey;
break;
default:
return -EINVAL;
}
- return r;
+ return r > 0 ? -EFAULT : r;
}
/* Section: device related */
@@ -2214,7 +2214,7 @@ static int kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
}
kvfree(keys);
- return r;
+ return r <= 0 ? r : -EFAULT;
}
static int kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
@@ -2276,7 +2276,7 @@ static int kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
kvm_s390_free_mmu_cache(mc);
out:
kvfree(keys);
- return r;
+ return r <= 0 ? r : -EFAULT;
}
/*
@@ -2386,7 +2386,7 @@ static int kvm_s390_set_cmma_bits(struct kvm *kvm,
set_bit(GMAP_FLAG_USES_CMM, &kvm->arch.gmap->flags);
- return r;
+ return r <= 0 ? r : -EFAULT;
}
/**
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index ad0ddc433a73..ea5a99537346 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -289,6 +289,7 @@ static int handle_iske(struct kvm_vcpu *vcpu)
static int handle_rrbe(struct kvm_vcpu *vcpu)
{
unsigned long gaddr;
+ union skey skey;
int reg1, reg2;
int rc;
@@ -307,12 +308,12 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
gaddr = kvm_s390_logical_to_effective(vcpu, gaddr);
gaddr = kvm_s390_real_to_abs(vcpu, gaddr);
scoped_guard(read_lock, &vcpu->kvm->mmu_lock)
- rc = dat_reset_reference_bit(vcpu->arch.gmap->asce, gpa_to_gfn(gaddr));
+ rc = dat_reset_reference_bit(vcpu->arch.gmap->asce, gpa_to_gfn(gaddr), &skey);
if (rc > 0)
return kvm_s390_inject_program_int(vcpu, rc);
if (rc < 0)
return rc;
- kvm_s390_set_psw_cc(vcpu, rc);
+ kvm_s390_set_psw_cc(vcpu, (skey.skey >> 1) & 3);
return 0;
}
--
2.55.0