linux-kernel - Re: [PATCH][v4] virt: tdx-guest: Don't free decrypted memory

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Message-ID: <c248f101-4c57-455f-9f70-53b3bd9602f0@intel.com>
Date: Mon, 2 Dec 2024 10:05:38 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
 "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
 "Li, Rongqing" <lirongqing@...du.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH][v4] virt: tdx-guest: Don't free decrypted memory

On 11/27/24 08:48, Edgecombe, Rick P wrote:
> On Wed, 2024-06-19 at 19:18 +0800, Li RongQing wrote:
>> In CoCo VMs it is possible for the untrusted host to cause
>> set_memory_decrypted() to fail such that an error is returned
>> and the resulting memory is shared. Callers need to take care
>> to handle these errors to avoid returning decrypted (shared)
>> memory to the page allocator, which could lead to functional
>> or security issues.
>>
>> Leak the decrypted memory when set_memory_decrypted() fails,
>> and don't need to print an error since set_memory_decrypted()
>> will call WARN_ONCE().
>>
>> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
>> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
>> Signed-off-by: Li RongQing <lirongqing@...du.com>
> It needs a Fixes tag.
> Fixes: f4738f56d1dc ("virt: tdx-guest: Add Quote generation support using
> TSM_REPORTS")
> 
> I think it is a worthwhile fix. Without it the guest can be tricked into freeing
> shared pages, or trying to execute from them and crashing.

Does this need a "Fixes" and cc:stable@?