Subject: CVE-2024-36909: Drivers: hv: vmbus: Don't free ring buffers that couldn't be re-encrypted

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

Drivers: hv: vmbus: Don't free ring buffers that couldn't be re-encrypted

In CoCo VMs it is possible for the untrusted host to cause
set_memory_encrypted() or 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.

The VMBus ring buffer code could free decrypted/shared pages if
set_memory_decrypted() fails. Check the decrypted field in the struct
vmbus_gpadl for the ring buffers to decide whether to free the memory.

The Linux kernel CVE team has assigned CVE-2024-36909 to this issue.

Affected and fixed versions
===========================

	Fixed in 6.1.91 with commit 2f622008bf78
	Fixed in 6.6.31 with commit 82f9e213b124
	Fixed in 6.8.10 with commit a9212a4e2963
	Fixed in 6.9 with commit 30d18df6567b

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-36909
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/hv/channel.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/2f622008bf784a9f5dd17baa19223cc2ac30a039
	https://git.kernel.org/stable/c/82f9e213b124a7d2bb5b16ea35d570260ef467e0
	https://git.kernel.org/stable/c/a9212a4e2963a7fbe3864ba33dc551d4ad8d0abb
	https://git.kernel.org/stable/c/30d18df6567be09c1433e81993e35e3da573ac48