[PATCH v2 5/5] Documentation: hyperv: Describe validation of the ring buffer indices

[Kameron Carr <kameroncarr@linux.microsoft.com>]

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.

Signed-off-by: Kameron Carr <kameroncarr@linux.microsoft.com>
---
 Documentation/virt/hyperv/coco.rst | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/hyperv/coco.rst b/Documentation/virt/hyperv/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 the host to the guest in a
 VMBus ring buffer, the length of the message is validated, and the message 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 and
+validate the read and write indices before using them to index into the ring
+buffer or to compute available space.
 
 Many drivers for VMBus devices have been "hardened" by adding code to fully
 validate messages received over VMBus, instead of assuming that Hyper-V is

-- 
2.45.4