Commit 19d6c5b8 authored by Claudio Imbrenda's avatar Claudio Imbrenda
Browse files

KVM: s390: vsie: Fix unshadowing while shadowing 



If shadowing causes the shadow gmap to get unshadowed, exit early to
prevent an attempt to dereference the parent pointer, which at this
point is NULL.

Opportunistically add some more checks to prevent NULL parents.

Fixes: a2c17f92 ("KVM: s390: New gmap code")
Fixes: e5f98a68 ("KVM: s390: Add some helper functions needed for vSIE")
Fixes: e38c884d ("KVM: s390: Switch to new gmap")
Signed-off-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
parent 0ec456b8

arch/s390/kvm/gaccess.c

+9 −0
Original line number Diff line number Diff line
@@ -1449,6 +1449,8 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union 
	pgste_set_unlock(ptep_h, pgste);

	if (rc)

		return rc;

	if (!sg->parent)

		return -EAGAIN;



	newpte = _pte(f->pfn, 0, !p, 0);

	if (!pgste_get_trylock(ptep, &pgste))
@@ -1476,6 +1478,9 @@ static int _do_shadow_crste(struct gmap *sg, gpa_t raddr, union crste *host, uni 
		return rc;



	do {

		/* _gmap_crstep_xchg_atomic() could have unshadowed this shadow gmap */

		if (!sg->parent)

			return -EAGAIN;

		oldcrste = READ_ONCE(*host);

		newcrste = _crste_fc1(f->pfn, oldcrste.h.tt, f->writable, !p);

		newcrste.s.fc1.d |= oldcrste.s.fc1.d;
@@ -1487,6 +1492,8 @@ static int _do_shadow_crste(struct gmap *sg, gpa_t raddr, union crste *host, uni 
		if (!newcrste.h.p && !f->writable)

			return -EOPNOTSUPP;

	} while (!_gmap_crstep_xchg_atomic(sg->parent, host, oldcrste, newcrste, f->gfn, false));

	if (!sg->parent)

		return -EAGAIN;



	newcrste = _crste_fc1(f->pfn, oldcrste.h.tt, 0, !p);

	gfn = gpa_to_gfn(raddr);
@@ -1531,6 +1538,8 @@ static int _gaccess_do_shadow(struct kvm_s390_mmu_cache *mc, struct gmap *sg, 
				       entries[i - 1].pfn, i, entries[i - 1].writable);

		if (rc)

			return rc;

		if (!sg->parent)

			return -EAGAIN;

	}



	rc = dat_entry_walk(NULL, entries[LEVEL_MEM].gfn, sg->parent->asce, DAT_WALK_LEAF,

arch/s390/kvm/gmap.c

+10 −1
Original line number Diff line number Diff line
@@ -1160,6 +1160,7 @@ struct gmap_protect_asce_top_level { 
static inline int __gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, struct gmap *sg,

						struct gmap_protect_asce_top_level *context)

{

	struct gmap *parent;

	int rc, i;



	guard(write_lock)(&sg->kvm->mmu_lock);
@@ -1167,7 +1168,12 @@ static inline int __gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, s 
	if (kvm_s390_array_needs_retry_safe(sg->kvm, context->seq, context->f))

		return -EAGAIN;



	scoped_guard(spinlock, &sg->parent->children_lock) {

	parent = READ_ONCE(sg->parent);

	if (!parent)

		return -EAGAIN;

	scoped_guard(spinlock, &parent->children_lock) {

		if (READ_ONCE(sg->parent) != parent)

			return -EAGAIN;

		for (i = 0; i < CRST_TABLE_PAGES; i++) {

			if (!context->f[i].valid)

				continue;
@@ -1250,6 +1256,9 @@ struct gmap *gmap_create_shadow(struct kvm_s390_mmu_cache *mc, struct gmap *pare 
	struct gmap *sg, *new;

	int rc;



	if (WARN_ON(!parent))

		return ERR_PTR(-EINVAL);



	scoped_guard(spinlock, &parent->children_lock) {

		sg = gmap_find_shadow(parent, asce, edat_level);

		if (sg) {