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charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: MN2PR02MB6863.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-Network-Message-Id: e40703b0-cf2a-43ac-4dac-08df2ed495ba X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Oct 2026 18:04:28.9514 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-CrossTenant-rms-persistedconsumerorg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR02MB6928 From: Kameron Carr Sent: Monday, October = 19, 2026 4:10 PM >=20 > Document that the guest must snapshot and validate the read and write > indices before using them to index into the ring buffer or to compute > the available space. >=20 > Signed-off-by: Kameron Carr Reviewed-by: Michael Kelley > --- > Documentation/virt/hyperv/coco.rst | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) >=20 > diff --git a/Documentation/virt/hyperv/coco.rst b/Documentation/virt/hype= rv/coco.rst > index 3231e51..3e20249 100644 > --- a/Documentation/virt/hyperv/coco.rst > +++ b/Documentation/virt/hyperv/coco.rst > @@ -200,7 +200,10 @@ validation is performed. For messages passed from th= e host > to the guest in a > VMBus ring buffer, the length of the message is validated, and the messa= ge is > copied into a temporary (encrypted) buffer for further validation and > processing. The copying adds a small amount of overhead, but is the only= way > -to protect against a malicious host. See hv_pkt_iter_first(). > +to protect against a malicious host. See hv_pkt_iter_first(). Similarly,= the > +ring buffer header is shared with the host, so the guest must snapshot a= nd > +validate the read and write indices before using them to index into the = ring > +buffer or to compute available space. >=20 > Many drivers for VMBus devices have been "hardened" by adding code to fu= lly > validate messages received over VMBus, instead of assuming that Hyper-V = is >=20 > -- > 2.45.4