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/xfs/xfs_hooks.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 fs/xfs/xfs_hooks.h (limited to 'fs/xfs/xfs_hooks.h') diff --git a/fs/xfs/xfs_hooks.h b/fs/xfs/xfs_hooks.h new file mode 100644 index 000000000..60b8a5831 --- /dev/null +++ b/fs/xfs/xfs_hooks.h @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2022-2024 Oracle. All Rights Reserved. + * Author: Darrick J. Wong + */ +#ifndef XFS_HOOKS_H_ +#define XFS_HOOKS_H_ + +#ifdef CONFIG_XFS_LIVE_HOOKS +struct xfs_hooks { + struct blocking_notifier_head head; +}; + +/* + * If jump labels are enabled in Kconfig, the static key uses nop sleds and + * code patching to eliminate the overhead of taking the rwsem in + * blocking_notifier_call_chain when there are no hooks configured. If not, + * the static key per-call overhead is an atomic read. Most arches that can + * handle XFS also support jump labels. + * + * Note: Patching the kernel code requires taking the cpu hotplug lock. Other + * parts of the kernel allocate memory with that lock held, which means that + * XFS callers cannot hold any locks that might be used by memory reclaim or + * writeback when calling the static_branch_{inc,dec} functions. + */ +# define DEFINE_STATIC_XFS_HOOK_SWITCH(name) \ + static DEFINE_STATIC_KEY_FALSE(name) +# define xfs_hooks_switch_on(name) static_branch_inc(name) +# define xfs_hooks_switch_off(name) static_branch_dec(name) +# define xfs_hooks_switched_on(name) static_branch_unlikely(name) + +struct xfs_hook { + /* This must come at the start of the structure. */ + struct notifier_block nb; +}; + +typedef int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action, + void *data); + +void xfs_hooks_init(struct xfs_hooks *chain); +int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook); +void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook); +int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action, + void *priv); + +static inline void xfs_hook_setup(struct xfs_hook *hook, notifier_fn_t fn) +{ + hook->nb.notifier_call = fn; + hook->nb.priority = 0; +} + +#else + +struct xfs_hooks { /* empty */ }; + +# define DEFINE_STATIC_XFS_HOOK_SWITCH(name) +# define xfs_hooks_switch_on(name) ((void)0) +# define xfs_hooks_switch_off(name) ((void)0) +# define xfs_hooks_switched_on(name) (false) + +# define xfs_hooks_init(chain) ((void)0) +# define xfs_hooks_call(chain, val, priv) (NOTIFY_DONE) +#endif + +#endif /* XFS_HOOKS_H_ */ -- cgit v1.3.1