selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/virt/acrn/introduction.rst b/Documentation/virt/acrn/introduction.rst
new file mode 100644
index 000000000..f8d081bc0
--- /dev/null
+++ b/Documentation/virt/acrn/introduction.rst
@@ -0,0 +1,43 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+ACRN Hypervisor Introduction
+============================
+
+The ACRN Hypervisor is a Type 1 hypervisor, running directly on bare-metal
+hardware. It has a privileged management VM, called Service VM, to manage User
+VMs and do I/O emulation.
+
+ACRN userspace is an application running in the Service VM that emulates
+devices for a User VM based on command line configurations. ACRN Hypervisor
+Service Module (HSM) is a kernel module in the Service VM which provides
+hypervisor services to the ACRN userspace.
+
+Below figure shows the architecture.
+
+::
+
+                Service VM                    User VM
+      +----------------------------+  |  +------------------+
+      |        +--------------+    |  |  |                  |
+      |        |ACRN userspace|    |  |  |                  |
+      |        +--------------+    |  |  |                  |
+      |-----------------ioctl------|  |  |                  |   ...
+      |kernel space   +----------+ |  |  |                  |
+      |               |   HSM    | |  |  | Drivers          |
+      |               +----------+ |  |  |                  |
+      +--------------------|-------+  |  +------------------+
+  +---------------------hypercall----------------------------------------+
+  |                         ACRN Hypervisor                              |
+  +----------------------------------------------------------------------+
+  |                          Hardware                                    |
+  +----------------------------------------------------------------------+
+
+ACRN userspace allocates memory for the User VM, configures and initializes the
+devices used by the User VM, loads the virtual bootloader, initializes the
+virtual CPU state and handles I/O request accesses from the User VM. It uses
+ioctls to communicate with the HSM. HSM implements hypervisor services by
+interacting with the ACRN Hypervisor via hypercalls. HSM exports a char device
+interface (/dev/acrn_hsm) to userspace.
+
+The ACRN hypervisor is open for contribution from anyone. The source repo is
+available at https://github.com/projectacrn/acrn-hypervisor.