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KVM: SVM: fix svn_pin_memory()'s use of get_user_pages_fast()

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There are two problems in svn_pin_memory():

1) The return value of get_user_pages_fast() is stored in an
unsigned long, although the declared return value is of type int.
This will not cause any symptoms, but it is misleading.
Fix this by changing the type of npinned to "int".

2) The number of pages passed into get_user_pages_fast() is stored
in an unsigned long, even though get_user_pages_fast() accepts an
int. This means that it is possible to silently overflow the number
of pages.

Fix this by adding a WARN_ON_ONCE() and an early error return. The
npages variable is left as an unsigned long for convenience in
checking for overflow.

Fixes: 89c5058090 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_UPDATE_DATA command")
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Message-Id: <20200526062207.1360225-2-jhubbard@nvidia.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
John Hubbard 2020-05-25 23:22:06 -07:00 committed by Paolo Bonzini
parent 1aef8161b3
commit 78824fabc7
1 changed files with 5 additions and 1 deletions
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6
arch/x86/kvm/svm/sev.c
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@ -313,7 +313,8 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
int write)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
unsigned long npages, npinned, size;
unsigned long npages, size;
int npinned;
unsigned long locked, lock_limit;
struct page **pages;
unsigned long first, last;
@ -333,6 +334,9 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
return NULL;
}
if (WARN_ON_ONCE(npages > INT_MAX))
return NULL;
/* Avoid using vmalloc for smaller buffers. */
size = npages * sizeof(struct page *);
if (size > PAGE_SIZE)