linux-kernel - [PATCH] x86/tdx: Fix data leak in mmio

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Message-ID: <20240826125304.1566719-1-kirill.shutemov@linux.intel.com>
Date: Mon, 26 Aug 2024 15:53:04 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org,
	linux-coco@...ts.linux.dev,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Sean Christopherson <seanjc@...gle.com>,
	stable@...r.kernel.org
Subject: [PATCH] x86/tdx: Fix data leak in mmio_read()

The mmio_read() function makes a TDVMCALL to retrieve MMIO data for an
address from the VMM.

Sean noticed that mmio_read() unintentionally exposes the value of an
initialized variable on the stack to the VMM.

Do not send the original value of *val to the VMM.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reported-by: Sean Christopherson <seanjc@...gle.com>
Fixes: 31d58c4e557d ("x86/tdx: Handle in-kernel MMIO")
Cc: stable@...r.kernel.org # v5.19+
---
 arch/x86/coco/tdx/tdx.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 078e2bac2553..da8b66dce0da 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -389,7 +389,6 @@ static bool mmio_read(int size, unsigned long addr, unsigned long *val)
 		.r12 = size,
 		.r13 = EPT_READ,
 		.r14 = addr,
-		.r15 = *val,
 	};
 
 	if (__tdx_hypercall(&args))
-- 
2.43.0