From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 15 Oct 2021 17:05:00 +0000 (-0400)
Subject: KVM: X86: fix lazy allocation of rmaps
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fa13843d1565d4c5b3aeb9be3343b313416bef46;p=linux.git

KVM: X86: fix lazy allocation of rmaps

If allocation of rmaps fails, but some of the pointers have already been written,
those pointers can be cleaned up when the memslot is freed, or even reused later
for another attempt at allocating the rmaps.  Therefore there is no need to
WARN, as done for example in memslot_rmap_alloc, but the allocation *must* be
skipped lest KVM will overwrite the previous pointer and will indeed leak memory.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aabd3a2ec1bc7..0c8b5129effdb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11392,7 +11392,8 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
 		int level = i + 1;
 		int lpages = __kvm_mmu_slot_lpages(slot, npages, level);
 
-		WARN_ON(slot->arch.rmap[i]);
+		if (slot->arch.rmap[i])
+			continue;
 
 		slot->arch.rmap[i] = kvcalloc(lpages, sz, GFP_KERNEL_ACCOUNT);
 		if (!slot->arch.rmap[i]) {