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 --- fs/cachefiles/main.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 fs/cachefiles/main.c (limited to 'fs/cachefiles/main.c') diff --git a/fs/cachefiles/main.c b/fs/cachefiles/main.c new file mode 100644 index 000000000..3f369c6f8 --- /dev/null +++ b/fs/cachefiles/main.c @@ -0,0 +1,93 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Network filesystem caching backend to use cache files on a premounted + * filesystem + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#define CREATE_TRACE_POINTS +#include "internal.h" + +unsigned cachefiles_debug; +module_param_named(debug, cachefiles_debug, uint, S_IWUSR | S_IRUGO); +MODULE_PARM_DESC(cachefiles_debug, "CacheFiles debugging mask"); + +MODULE_DESCRIPTION("Mounted-filesystem based cache"); +MODULE_AUTHOR("Red Hat, Inc."); +MODULE_LICENSE("GPL"); + +struct kmem_cache *cachefiles_object_jar; + +static struct miscdevice cachefiles_dev = { + .minor = MISC_DYNAMIC_MINOR, + .name = "cachefiles", + .fops = &cachefiles_daemon_fops, +}; + +/* + * initialise the fs caching module + */ +static int __init cachefiles_init(void) +{ + int ret; + + ret = cachefiles_register_error_injection(); + if (ret < 0) + goto error_einj; + ret = misc_register(&cachefiles_dev); + if (ret < 0) + goto error_dev; + + /* create an object jar */ + ret = -ENOMEM; + cachefiles_object_jar = + kmem_cache_create("cachefiles_object_jar", + sizeof(struct cachefiles_object), + 0, SLAB_HWCACHE_ALIGN, NULL); + if (!cachefiles_object_jar) { + pr_notice("Failed to allocate an object jar\n"); + goto error_object_jar; + } + + pr_info("Loaded\n"); + return 0; + +error_object_jar: + misc_deregister(&cachefiles_dev); +error_dev: + cachefiles_unregister_error_injection(); +error_einj: + pr_err("failed to register: %d\n", ret); + return ret; +} + +fs_initcall(cachefiles_init); + +/* + * clean up on module removal + */ +static void __exit cachefiles_exit(void) +{ + pr_info("Unloading\n"); + + kmem_cache_destroy(cachefiles_object_jar); + misc_deregister(&cachefiles_dev); + cachefiles_unregister_error_injection(); +} + +module_exit(cachefiles_exit); -- cgit v1.3.1