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 --- tools/testing/radix-tree/xarray.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 tools/testing/radix-tree/xarray.c (limited to 'tools/testing/radix-tree/xarray.c') diff --git a/tools/testing/radix-tree/xarray.c b/tools/testing/radix-tree/xarray.c new file mode 100644 index 000000000..253208a85 --- /dev/null +++ b/tools/testing/radix-tree/xarray.c @@ -0,0 +1,30 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * xarray.c: Userspace shim for XArray test-suite + * Copyright (c) 2018 Matthew Wilcox + */ + +#include "xarray-shared.h" +#include "test.h" + +#undef XA_DEBUG +#include "../../../lib/test_xarray.c" + +void xarray_tests(void) +{ + xarray_checks(); + xarray_exit(); +} + +int __weak main(void) +{ + rcu_register_thread(); + radix_tree_init(); + xarray_tests(); + radix_tree_cpu_dead(1); + rcu_barrier(); + if (nr_allocated) + printf("nr_allocated = %d\n", nr_allocated); + rcu_unregister_thread(); + return 0; +} -- cgit v1.3.1