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 --- scripts/mod/mk_elfconfig.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 scripts/mod/mk_elfconfig.c (limited to 'scripts/mod/mk_elfconfig.c') diff --git a/scripts/mod/mk_elfconfig.c b/scripts/mod/mk_elfconfig.c new file mode 100644 index 000000000..e8cee4e4b --- /dev/null +++ b/scripts/mod/mk_elfconfig.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +int +main(int argc, char **argv) +{ + unsigned char ei[EI_NIDENT]; + + if (fread(ei, 1, EI_NIDENT, stdin) != EI_NIDENT) { + fprintf(stderr, "Error: input truncated\n"); + return 1; + } + if (memcmp(ei, ELFMAG, SELFMAG) != 0) { + fprintf(stderr, "Error: not ELF\n"); + return 1; + } + switch (ei[EI_CLASS]) { + case ELFCLASS32: + printf("#define KERNEL_ELFCLASS ELFCLASS32\n"); + break; + case ELFCLASS64: + printf("#define KERNEL_ELFCLASS ELFCLASS64\n"); + break; + default: + exit(1); + } + + return 0; +} -- cgit v1.3.1