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/perf/util/pstack.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 tools/perf/util/pstack.c (limited to 'tools/perf/util/pstack.c') diff --git a/tools/perf/util/pstack.c b/tools/perf/util/pstack.c new file mode 100644 index 000000000..141ffa129 --- /dev/null +++ b/tools/perf/util/pstack.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Simple pointer stack + * + * (c) 2010 Arnaldo Carvalho de Melo + */ + +#include "pstack.h" +#include "debug.h" +#include +#include +#include +#include + +struct pstack { + unsigned short top; + unsigned short max_nr_entries; + void *entries[]; +}; + +struct pstack *pstack__new(unsigned short max_nr_entries) +{ + struct pstack *pstack = zalloc((sizeof(*pstack) + + max_nr_entries * sizeof(void *))); + if (pstack != NULL) + pstack->max_nr_entries = max_nr_entries; + return pstack; +} + +void pstack__delete(struct pstack *pstack) +{ + free(pstack); +} + +bool pstack__empty(const struct pstack *pstack) +{ + return pstack->top == 0; +} + +void pstack__remove(struct pstack *pstack, void *key) +{ + unsigned short i = pstack->top, last_index = pstack->top - 1; + + while (i-- != 0) { + if (pstack->entries[i] == key) { + if (i < last_index) + memmove(pstack->entries + i, + pstack->entries + i + 1, + (last_index - i) * sizeof(void *)); + --pstack->top; + return; + } + } + pr_err("%s: %p not on the pstack!\n", __func__, key); +} + +void pstack__push(struct pstack *pstack, void *key) +{ + if (pstack->top == pstack->max_nr_entries) { + pr_err("%s: top=%d, overflow!\n", __func__, pstack->top); + return; + } + pstack->entries[pstack->top++] = key; +} + +void *pstack__peek(struct pstack *pstack) +{ + if (pstack->top == 0) + return NULL; + return pstack->entries[pstack->top - 1]; +} -- cgit v1.3.1