* [PATCH] x86/tdx: Fix data leak in mmio_read()
@ 2024-08-26 12:53 Kirill A. Shutemov
2024-08-26 16:41 ` Dave Hansen
0 siblings, 1 reply; 3+ messages in thread
From: Kirill A. Shutemov @ 2024-08-26 12:53 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin
Cc: linux-kernel, linux-coco, Kirill A. Shutemov, Sean Christopherson,
stable
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@linux.intel.com>
Reported-by: Sean Christopherson <seanjc@google.com>
Fixes: 31d58c4e557d ("x86/tdx: Handle in-kernel MMIO")
Cc: stable@vger.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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/tdx: Fix data leak in mmio_read()
2024-08-26 12:53 [PATCH] x86/tdx: Fix data leak in mmio_read() Kirill A. Shutemov
@ 2024-08-26 16:41 ` Dave Hansen
2024-08-26 19:44 ` Kirill A. Shutemov
0 siblings, 1 reply; 3+ messages in thread
From: Dave Hansen @ 2024-08-26 16:41 UTC (permalink / raw)
To: Kirill A. Shutemov, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin
Cc: linux-kernel, linux-coco, Sean Christopherson, stable
On 8/26/24 05:53, Kirill A. Shutemov wrote:
> 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.
The key to this is that 'val' is only used for the _return_ value, right?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/tdx: Fix data leak in mmio_read()
2024-08-26 16:41 ` Dave Hansen
@ 2024-08-26 19:44 ` Kirill A. Shutemov
0 siblings, 0 replies; 3+ messages in thread
From: Kirill A. Shutemov @ 2024-08-26 19:44 UTC (permalink / raw)
To: Dave Hansen
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, linux-kernel, linux-coco, Sean Christopherson,
stable
On Mon, Aug 26, 2024 at 09:41:49AM -0700, Dave Hansen wrote:
> On 8/26/24 05:53, Kirill A. Shutemov wrote:
> > 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.
>
> The key to this is that 'val' is only used for the _return_ value, right?
Correct.
--
Kiryl Shutsemau / Kirill A. Shutemov
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-08-26 12:53 [PATCH] x86/tdx: Fix data leak in mmio_read() Kirill A. Shutemov
2024-08-26 16:41 ` Dave Hansen
2024-08-26 19:44 ` Kirill A. Shutemov
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