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Date: Fri, 14 Jun 2024 09:03:22 -0700
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Subject: Re: [PATCH v11 8/8] x86/vmware: Add TDX hypercall support
To: Alexey Makhalov <alexey.makhalov@broadcom.com>,
 linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, bp@alien8.de,
 hpa@zytor.com, dave.hansen@linux.intel.com, mingo@redhat.com,
 tglx@linutronix.de
Cc: x86@kernel.org, netdev@vger.kernel.org, richardcochran@gmail.com,
 linux-input@vger.kernel.org, dmitry.torokhov@gmail.com, zackr@vmware.com,
 linux-graphics-maintainer@vmware.com, pv-drivers@vmware.com,
 timothym@vmware.com, akaher@vmware.com, dri-devel@lists.freedesktop.org,
 daniel@ffwll.ch, airlied@gmail.com, tzimmermann@suse.de, mripard@kernel.org,
 maarten.lankhorst@linux.intel.com, horms@kernel.org,
 kirill.shutemov@linux.intel.com, Tim Merrifield <tim.merrifield@broadcom.com>
References: <20240613191650.9913-1-alexey.makhalov@broadcom.com>
 <20240613191650.9913-9-alexey.makhalov@broadcom.com>
From: Dave Hansen <dave.hansen@intel.com>
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In-Reply-To: <20240613191650.9913-9-alexey.makhalov@broadcom.com>
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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.