| Message ID | 20200526062207.1360225-2-jhubbard@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: SVM: convert get_user_pages() --> pin_user_pages(), bug fixes | expand |
John Hubbard <jhubbard@nvidia.com> writes: > 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 <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> > --- > 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 89f7f3aebd31..9693db1af57c 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; > + I bit unrelated to this patch, but callers of sev_pin_memory() treat NULL differently: sev_launch_secret()/svm_register_enc_region() return -ENOMEM sev_dbg_crypt() returns -EFAULT Should we switch to ERR_PTR() to preserve the error? > /* Avoid using vmalloc for smaller buffers. */ > size = npages * sizeof(struct page *); > if (size > PAGE_SIZE) Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
On 2020-05-26 00:33, Vitaly Kuznetsov wrote: ... > I bit unrelated to this patch, but callers of sev_pin_memory() treat > NULL differently: > > sev_launch_secret()/svm_register_enc_region() return -ENOMEM > sev_dbg_crypt() returns -EFAULT > > Should we switch to ERR_PTR() to preserve the error? > >> /* Avoid using vmalloc for smaller buffers. */ >> size = npages * sizeof(struct page *); >> if (size > PAGE_SIZE) > > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> > Thanks for the review, Vitaly. If anyone is able to do any run-time testing of this patch and also patch 2/2, then I think a maintainer would be more willing to pick them up. Any testing help there is greatly appreciated! thanks,
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 89f7f3aebd31..9693db1af57c 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)
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 <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> --- arch/x86/kvm/svm/sev.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)