KVM: Fix out of range accesses to memslots (0774a964) · Commits · 戴 / test

Reset the LRU slot if it becomes invalid when deleting a memslot to fix an out-of-bounds/use-after-free access when searching through memslots. Explicitly check for there being no used slots in search_memslots(), and in the caller of s390's approximation variant. Fixes: ("KVM: Dynamically size memslot array based on number of used slots") Reported-by:

Qian Cai <cai@lca.pw> Cc: Peter Xu <peterx@redhat.com> Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200320205546.2396-2-sean.j.christopherson@intel.com> Acked-by:

Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/s390/kvm/kvm-s390.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2002,6 +2002,9 @@ static int kvm_s390_get_cmma(struct kvm kvm, struct kvm_s390_cmma_log args,
		struct kvm_memslots *slots = kvm_memslots(kvm);
		struct kvm_memory_slot *ms;

		if (unlikely(!slots->used_slots))
		return 0;

		cur_gfn = kvm_s390_next_dirty_cmma(slots, args->start_gfn);
		ms = gfn_to_memslot(kvm, cur_gfn);
		args->count = 0;

include/linux/kvm_host.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -1032,6 +1032,9 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn)
		int slot = atomic_read(&slots->lru_slot);
		struct kvm_memory_slot *memslots = slots->memslots;

		if (unlikely(!slots->used_slots))
		return NULL;

		if (gfn >= memslots[slot].base_gfn &&
		gfn < memslots[slot].base_gfn + memslots[slot].npages)
		return &memslots[slot];

virt/kvm/kvm_main.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -882,6 +882,9 @@ static inline void kvm_memslot_delete(struct kvm_memslots *slots,

		slots->used_slots--;

		if (atomic_read(&slots->lru_slot) >= slots->used_slots)
		atomic_set(&slots->lru_slot, 0);

		for (i = slots->id_to_index[memslot->id]; i < slots->used_slots; i++) {
		mslots[i] = mslots[i + 1];
		slots->id_to_index[mslots[i].id] = i;

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