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[4.9,3/4] KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped()

Message ID Ye7Xa599VFy2WEkC@decadent.org.uk
State New
Headers show
Series [4.9,1/4] mm: add follow_pte_pmd() | expand

Commit Message

Ben Hutchings Jan. 24, 2022, 4:44 p.m. UTC 
From: Sean Christopherson <seanjc@google.com>

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: add6a0cd1c5b ("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: Ben Hutchings <ben@decadent.org.uk>
---
 virt/kvm/kvm_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2729704f836e..dc7b60c81039 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1518,7 +1518,7 @@  static int hva_to_pfn_remapped(struct vm_area_struct *vma,
 			       bool write_fault, bool *writable,
 			       kvm_pfn_t *p_pfn)
 {
-	unsigned long pfn;
+	kvm_pfn_t pfn;
 	pte_t *ptep;
 	spinlock_t *ptl;
 	int r;