4.20-stable review patch. If anyone has any objections, please let me know.
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From: Tom Roeder tmroeder@google.com
commit 3a33d030daaa7c507e1c12d5adcf828248429593 upstream.
This changes the allocation of cached_vmcs12 to use kzalloc instead of kmalloc. This removes the information leak found by Syzkaller (see Reported-by) in this case and prevents similar leaks from happening based on cached_vmcs12.
It also changes vmx_get_nested_state to copy out the full 4k VMCS12_SIZE in copy_to_user rather than only the size of the struct.
Tested: rebuilt against head, booted, and ran the syszkaller repro https://syzkaller.appspot.com/text?tag=ReproC&x=174efca3400000 without observing any problems.
Reported-by: syzbot+ded1696f6b50b615b630@syzkaller.appspotmail.com Fixes: 8fcc4b5923af5de58b80b53a069453b135693304 Cc: stable@vger.kernel.org Signed-off-by: Tom Roeder tmroeder@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/vmx.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8315,11 +8315,11 @@ static int enter_vmx_operation(struct kv if (r < 0) goto out_vmcs02;
- vmx->nested.cached_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL); + vmx->nested.cached_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL); if (!vmx->nested.cached_vmcs12) goto out_cached_vmcs12;
- vmx->nested.cached_shadow_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL); + vmx->nested.cached_shadow_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL); if (!vmx->nested.cached_shadow_vmcs12) goto out_cached_shadow_vmcs12;
@@ -14853,13 +14853,17 @@ static int vmx_get_nested_state(struct k copy_shadow_to_vmcs12(vmx); }
- if (copy_to_user(user_kvm_nested_state->data, vmcs12, sizeof(*vmcs12))) + /* + * Copy over the full allocated size of vmcs12 rather than just the size + * of the struct. + */ + if (copy_to_user(user_kvm_nested_state->data, vmcs12, VMCS12_SIZE)) return -EFAULT;
if (nested_cpu_has_shadow_vmcs(vmcs12) && vmcs12->vmcs_link_pointer != -1ull) { if (copy_to_user(user_kvm_nested_state->data + VMCS12_SIZE, - get_shadow_vmcs12(vcpu), sizeof(*vmcs12))) + get_shadow_vmcs12(vcpu), VMCS12_SIZE)) return -EFAULT; }