linux-kernel - [PATCH 5.17 1003/1126] KVM: avoid double put

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Message-Id: <20220405070436.931601245@linuxfoundation.org>
Date:   Tue,  5 Apr 2022 09:29:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Woodhouse <dwmw2@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.17 1003/1126] KVM: avoid double put_page with gfn-to-pfn cache

From: David Woodhouse <dwmw@...zon.co.uk>

commit 79593c086eb95eb2886f36ee6f78a1d6845e1bdf upstream.

If the cache's user host virtual address becomes invalid, there
is still a path from kvm_gfn_to_pfn_cache_refresh() where __release_gpc()
could release the pfn but the gpc->pfn field has not been overwritten
with an error value.  If this happens, kvm_gfn_to_pfn_cache_unmap will
call put_page again on the same page.

Cc: stable@...r.kernel.org
Fixes: 982ed0de4753 ("KVM: Reinstate gfn_to_pfn_cache with invalidation support")
Signed-off-by: David Woodhouse <dwmw2@...radead.org>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 virt/kvm/pfncache.c |    1 +
 1 file changed, 1 insertion(+)

--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -191,6 +191,7 @@ int kvm_gfn_to_pfn_cache_refresh(struct
 		gpc->uhva = gfn_to_hva_memslot(gpc->memslot, gfn);
 
 		if (kvm_is_error_hva(gpc->uhva)) {
+			gpc->pfn = KVM_PFN_ERR_FAULT;
 			ret = -EFAULT;
 			goto out;
 		}