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KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped()

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commit a9545779ee9e9e103648f6f2552e73cfe808d0f4 upstream.

Use kvm_pfn_t, a.k.a. u64, for the local 'pfn' variable when retrieving
a so called "remapped" hva/pfn pair.  In theory, the hva could resolve to
a pfn in high memory on a 32-bit kernel.

This bug was inadvertantly exposed by commit bd2fae8da794 ("KVM: do not
assume PTE is writable after follow_pfn"), which added an error PFN value
to the mix, causing gcc to comlain about overflowing the unsigned long.

  arch/x86/kvm/../../../virt/kvm/kvm_main.c: In function ‘hva_to_pfn_remapped’:
  include/linux/kvm_host.h:89:30: error: conversion from ‘long long unsigned int’
                                  to ‘long unsigned int’ changes value from
                                  ‘9218868437227405314’ to ‘2’ [-Werror=overflow]
   89 | #define KVM_PFN_ERR_RO_FAULT (KVM_PFN_ERR_MASK + 2)
      |                              ^
virt/kvm/kvm_main.c:1935:9: note: in expansion of macro ‘KVM_PFN_ERR_RO_FAULT’

Cc: stable@vger.kernel.org
Fixes: add6a0cd1c ("KVM: MMU: try to fix up page faults before giving up")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210208201940.1258328-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-02-08 12:19:40 -08:00 committed by Greg Kroah-Hartman
parent a42150f1c9
commit 3320aa64c3
1 changed files with 1 additions and 1 deletions
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virt/kvm/kvm_main.c
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@ -1888,7 +1888,7 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
bool write_fault, bool *writable, bool write_fault, bool *writable,
kvm_pfn_t *p_pfn) kvm_pfn_t *p_pfn)
{ {
unsigned long pfn; kvm_pfn_t pfn;
pte_t *ptep; pte_t *ptep;
spinlock_t *ptl; spinlock_t *ptl;
int r; int r;