From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock 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 Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- Documentation/dev-tools/testing-devices.rst | 47 +++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) create mode 100644 Documentation/dev-tools/testing-devices.rst (limited to 'Documentation/dev-tools/testing-devices.rst') diff --git a/Documentation/dev-tools/testing-devices.rst b/Documentation/dev-tools/testing-devices.rst new file mode 100644 index 000000000..ab26adb99 --- /dev/null +++ b/Documentation/dev-tools/testing-devices.rst @@ -0,0 +1,47 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright (c) 2024 Collabora Ltd + +============================= +Device testing with kselftest +============================= + + +There are a few different kselftests available for testing devices generically, +with some overlap in coverage and different requirements. This document aims to +give an overview of each one. + +Note: Paths in this document are relative to the kselftest folder +(``tools/testing/selftests``). + +Device oriented kselftests: + +* Devicetree (``dt``) + + * **Coverage**: Probe status for devices described in Devicetree + * **Requirements**: None + +* Error logs (``devices/error_logs``) + + * **Coverage**: Error (or more critical) log messages presence coming from any + device + * **Requirements**: None + +* Discoverable bus (``devices/probe``) + + * **Coverage**: Presence and probe status of USB or PCI devices that have been + described in the reference file + * **Requirements**: Manually describe the devices that should be tested in a + YAML reference file (see ``devices/probe/boards/google,spherion.yaml`` for + an example) + +* Exist (``devices/exist``) + + * **Coverage**: Presence of all devices + * **Requirements**: Generate the reference (see ``devices/exist/README.rst`` + for details) on a known-good kernel + +Therefore, the suggestion is to enable the error log and devicetree tests on all +(DT-based) platforms, since they don't have any requirements. Then to greatly +improve coverage, generate the reference for each platform and enable the exist +test. The discoverable bus test can be used to verify the probe status of +specific USB or PCI devices, but is probably not worth it for most cases. -- cgit v1.3.1