Re: [PATCH v11 8/8] x86/vmware: Add TDX hypercall support

Borislav Petkov
2024-06-14T16:14:42Z

On Fri, Jun 14, 2024 at 09:03:22AM -0700, Dave Hansen wrote:
> On 6/13/24 12:16, Alexey Makhalov wrote:
> > +unsigned long vmware_tdx_hypercall(unsigned long cmd,
> > + unsigned long in1, unsigned long in3,
> > + unsigned long in4, unsigned long in5,
> > + u32 *out1, u32 *out2, u32 *out3,
> > + u32 *out4, u32 *out5)
> > +{
> > + struct tdx_module_args args;
> > +
> > + if (!hypervisor_is_type(X86_HYPER_VMWARE)) {
> > + pr_warn_once("Incorrect usage\n");
> > + return ULONG_MAX;
> > + }
> > +
> > + if (cmd & ~VMWARE_CMD_MASK) {
> > + pr_warn_once("Out of range command %lx\n", cmd);
> > + return ULONG_MAX;
> > + }
> > +
> > + args.rbx = in1;
> > + args.rdx = in3;
> > + args.rsi = in4;
> > + args.rdi = in5;
> > + args.r10 = VMWARE_TDX_VENDOR_LEAF;
> > + args.r11 = VMWARE_TDX_HCALL_FUNC;
> > + args.r12 = VMWARE_HYPERVISOR_MAGIC;
> > + args.r13 = cmd;
> > + args.r15 = 0; /* CPL */
>
> I believe this leaks stack data into the hypervisor. Or did I miss the
> zeroing of rcx/r8/r9/r14?
>
> You need to zero out all of 'args' somehow.

You mean like this:

struct tdx_module_args args = {};

?

--
Regards/Gruss,
Boris.