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 --- .../devicetree/dynamic-resolution-notes.rst | 27 ++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 Documentation/devicetree/dynamic-resolution-notes.rst (limited to 'Documentation/devicetree/dynamic-resolution-notes.rst') diff --git a/Documentation/devicetree/dynamic-resolution-notes.rst b/Documentation/devicetree/dynamic-resolution-notes.rst new file mode 100644 index 000000000..f81ad8daa --- /dev/null +++ b/Documentation/devicetree/dynamic-resolution-notes.rst @@ -0,0 +1,27 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================= +Devicetree Dynamic Resolver Notes +================================= + +This document describes the implementation of the in-kernel +DeviceTree resolver, residing in drivers/of/resolver.c + +How the resolver works +---------------------- + +The resolver is given as an input an arbitrary tree compiled with the +proper dtc option and having a /plugin/ tag. This generates the +appropriate __fixups__ & __local_fixups__ nodes. + +In sequence the resolver works by the following steps: + +1. Get the maximum device tree phandle value from the live tree + 1. +2. Adjust all the local phandles of the tree to resolve by that amount. +3. Using the __local__fixups__ node information adjust all local references + by the same amount. +4. For each property in the __fixups__ node locate the node it references + in the live tree. This is the label used to tag the node. +5. Retrieve the phandle of the target of the fixup. +6. For each fixup in the property locate the node:property:offset location + and replace it with the phandle value. -- cgit v1.3.1