From 78824fabc72e5e37d51e6e567fde70a4fc41a6d7 Mon Sep 17 00:00:00 2001 From: John Hubbard Date: Mon, 25 May 2020 23:22:06 -0700 Subject: [PATCH] KVM: SVM: fix svn_pin_memory()'s use of get_user_pages_fast() 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: 89c505809052 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_UPDATE_DATA command") Cc: Ingo Molnar Cc: Borislav Petkov Cc: Thomas Gleixner Cc: Paolo Bonzini Cc: Sean Christopherson Cc: Vitaly Kuznetsov Cc: Wanpeng Li Cc: Jim Mattson Cc: Joerg Roedel Cc: H. Peter Anvin Cc: x86@kernel.org Cc: kvm@vger.kernel.org Signed-off-by: John Hubbard Message-Id: <20200526062207.1360225-2-jhubbard@nvidia.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/sev.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 5573a97..ceeee4b 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -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) -- 2.7.4