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 --- samples/kdb/kdb_hello.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 samples/kdb/kdb_hello.c (limited to 'samples/kdb/kdb_hello.c') diff --git a/samples/kdb/kdb_hello.c b/samples/kdb/kdb_hello.c new file mode 100644 index 000000000..82736e5a5 --- /dev/null +++ b/samples/kdb/kdb_hello.c @@ -0,0 +1,58 @@ +/* + * Created by: Jason Wessel + * + * Copyright (c) 2010 Wind River Systems, Inc. All Rights Reserved. + * + * This file is licensed under the terms of the GNU General Public + * License version 2. This program is licensed "as is" without any + * warranty of any kind, whether express or implied. + */ + +#include +#include + +/* + * All kdb shell command call backs receive argc and argv, where + * argv[0] is the command the end user typed + */ +static int kdb_hello_cmd(int argc, const char **argv) +{ + if (argc > 1) + return KDB_ARGCOUNT; + + if (argc) + kdb_printf("Hello %s.\n", argv[1]); + else + kdb_printf("Hello world!\n"); + + return 0; +} + +static kdbtab_t hello_cmd = { + .name = "hello", + .func = kdb_hello_cmd, + .usage = "[string]", + .help = "Say Hello World or Hello [string]", +}; + +static int __init kdb_hello_cmd_init(void) +{ + /* + * Registration of a dynamically added kdb command is done with + * kdb_register(). + */ + kdb_register(&hello_cmd); + return 0; +} + +static void __exit kdb_hello_cmd_exit(void) +{ + kdb_unregister(&hello_cmd); +} + +module_init(kdb_hello_cmd_init); +module_exit(kdb_hello_cmd_exit); + +MODULE_AUTHOR("WindRiver"); +MODULE_DESCRIPTION("KDB example to add a hello command"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1