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

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Message-ID: <844ef200-aabe-4497-85c9-44fc46c9133a@intel.com>
Date: Fri, 14 Jun 2024 09:03:22 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Alexey Makhalov <alexey.makhalov@...adcom.com>,
 linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev, bp@...en8.de,
 hpa@...or.com, dave.hansen@...ux.intel.com, mingo@...hat.com,
 tglx@...utronix.de
Cc: x86@...nel.org, netdev@...r.kernel.org, richardcochran@...il.com,
 linux-input@...r.kernel.org, dmitry.torokhov@...il.com, zackr@...are.com,
 linux-graphics-maintainer@...are.com, pv-drivers@...are.com,
 timothym@...are.com, akaher@...are.com, dri-devel@...ts.freedesktop.org,
 daniel@...ll.ch, airlied@...il.com, tzimmermann@...e.de, mripard@...nel.org,
 maarten.lankhorst@...ux.intel.com, horms@...nel.org,
 kirill.shutemov@...ux.intel.com, Tim Merrifield <tim.merrifield@...adcom.com>
Subject: Re: [PATCH v11 8/8] x86/vmware: Add TDX hypercall support

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.