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/objtool/builtin-klp.c | 54 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 tools/objtool/builtin-klp.c (limited to 'tools/objtool/builtin-klp.c') diff --git a/tools/objtool/builtin-klp.c b/tools/objtool/builtin-klp.c new file mode 100644 index 000000000..58c3b9bda --- /dev/null +++ b/tools/objtool/builtin-klp.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#include +#include +#include +#include +#include +#include + +struct subcmd { + const char *name; + const char *description; + int (*fn)(int, const char **); +}; + +static struct subcmd subcmds[] = { + { "checksum", "Generate per-function checksums", cmd_klp_checksum, }, + { "diff", "Generate binary diff of two object files", cmd_klp_diff, }, + { "post-link", "Finalize klp symbols/relocs after module linking", cmd_klp_post_link, }, +}; + +static void cmd_klp_usage(void) +{ + fprintf(stderr, "usage: objtool klp []\n\n"); + fprintf(stderr, "Subcommands:\n"); + + for (int i = 0; i < ARRAY_SIZE(subcmds); i++) { + struct subcmd *cmd = &subcmds[i]; + + fprintf(stderr, " %s\t%s\n", cmd->name, cmd->description); + } + + exit(1); +} + +int cmd_klp(int argc, const char **argv) +{ + argc--; + argv++; + + if (!argc) + cmd_klp_usage(); + + if (argc) { + for (int i = 0; i < ARRAY_SIZE(subcmds); i++) { + struct subcmd *cmd = &subcmds[i]; + + if (!strcmp(cmd->name, argv[0])) + return cmd->fn(argc, argv); + } + } + + cmd_klp_usage(); + return 0; +} -- cgit v1.3.1