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 --- drivers/nvmem/layouts/fixed-layout.c | 58 ++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 drivers/nvmem/layouts/fixed-layout.c (limited to 'drivers/nvmem/layouts/fixed-layout.c') diff --git a/drivers/nvmem/layouts/fixed-layout.c b/drivers/nvmem/layouts/fixed-layout.c new file mode 100644 index 000000000..635d448b3 --- /dev/null +++ b/drivers/nvmem/layouts/fixed-layout.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright 2026 Bootlin + * + * Authors: Mathieu Dubois-Briand + */ + +#include +#include + +#include "../internals.h" + +static int fixed_layout_add_cells(struct nvmem_layout *layout) +{ + struct device_node *np; + int ret; + + np = of_nvmem_layout_get_container(layout->nvmem); + if (!np) + return -ENOENT; + + ret = nvmem_add_cells_from_dt(layout->nvmem, np); + of_node_put(np); + + return ret; +} + +static int fixed_layout_probe(struct nvmem_layout *layout) +{ + layout->add_cells = fixed_layout_add_cells; + + return nvmem_layout_register(layout); +} + +static void fixed_layout_remove(struct nvmem_layout *layout) +{ + nvmem_layout_unregister(layout); +} + +static const struct of_device_id fixed_layout_of_match_table[] = { + { .compatible = "fixed-layout", }, + {}, +}; + +static struct nvmem_layout_driver fixed_layout_layout = { + .driver = { + .name = "fixed-layout", + .of_match_table = fixed_layout_of_match_table, + }, + .probe = fixed_layout_probe, + .remove = fixed_layout_remove, +}; +module_nvmem_layout_driver(fixed_layout_layout); + +MODULE_AUTHOR("Mathieu Dubois-Briand"); +MODULE_LICENSE("GPL"); +MODULE_DEVICE_TABLE(of, fixed_layout_of_match_table); +MODULE_DESCRIPTION("NVMEM fixed-layout driver"); -- cgit v1.3.1