selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 468 insertions, 0 deletions

diff --git a/fs/dlm/recoverd.c b/fs/dlm/recoverd.c
new file mode 100644
index 000000000..12272a8f6
--- /dev/null
+++ b/fs/dlm/recoverd.c
@@ -0,0 +1,468 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2011 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#include "dlm_internal.h"
+#include "lockspace.h"
+#include "member.h"
+#include "dir.h"
+#include "ast.h"
+#include "recover.h"
+#include "lowcomms.h"
+#include "lock.h"
+#include "requestqueue.h"
+#include "recoverd.h"
+
+static int dlm_create_masters_list(struct dlm_ls *ls)
+{
+	struct dlm_rsb *r;
+	int error = 0;
+
+	write_lock_bh(&ls->ls_masters_lock);
+	if (!list_empty(&ls->ls_masters_list)) {
+		log_error(ls, "root list not empty");
+		error = -EINVAL;
+		goto out;
+	}
+
+	read_lock_bh(&ls->ls_rsbtbl_lock);
+	list_for_each_entry(r, &ls->ls_slow_active, res_slow_list) {
+		if (r->res_nodeid)
+			continue;
+
+		list_add(&r->res_masters_list, &ls->ls_masters_list);
+		dlm_hold_rsb(r);
+	}
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
+ out:
+	write_unlock_bh(&ls->ls_masters_lock);
+	return error;
+}
+
+static void dlm_release_masters_list(struct dlm_ls *ls)
+{
+	struct dlm_rsb *r, *safe;
+
+	write_lock_bh(&ls->ls_masters_lock);
+	list_for_each_entry_safe(r, safe, &ls->ls_masters_list, res_masters_list) {
+		list_del_init(&r->res_masters_list);
+		dlm_put_rsb(r);
+	}
+	write_unlock_bh(&ls->ls_masters_lock);
+}
+
+static void dlm_create_root_list(struct dlm_ls *ls, struct list_head *root_list)
+{
+	struct dlm_rsb *r;
+
+	read_lock_bh(&ls->ls_rsbtbl_lock);
+	list_for_each_entry(r, &ls->ls_slow_active, res_slow_list) {
+		list_add(&r->res_root_list, root_list);
+		dlm_hold_rsb(r);
+	}
+
+	WARN_ON_ONCE(!list_empty(&ls->ls_slow_inactive));
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
+}
+
+static void dlm_release_root_list(struct list_head *root_list)
+{
+	struct dlm_rsb *r, *safe;
+
+	list_for_each_entry_safe(r, safe, root_list, res_root_list) {
+		list_del_init(&r->res_root_list);
+		dlm_put_rsb(r);
+	}
+}
+
+/* If the start for which we're re-enabling locking (seq) has been superseded
+   by a newer stop (ls_recover_seq), we need to leave locking disabled.
+
+   We suspend dlm_recv threads here to avoid the race where dlm_recv a) sees
+   locking stopped and b) adds a message to the requestqueue, but dlm_recoverd
+   enables locking and clears the requestqueue between a and b. */
+
+static int enable_locking(struct dlm_ls *ls, uint64_t seq)
+{
+	int error = -EINTR;
+
+	write_lock_bh(&ls->ls_recv_active);
+
+	spin_lock_bh(&ls->ls_recover_lock);
+	if (ls->ls_recover_seq == seq) {
+		set_bit(LSFL_RUNNING, &ls->ls_flags);
+		/* Schedule next timer if recovery put something on inactive.
+		 *
+		 * The rsbs that was queued while recovery on toss hasn't
+		 * started yet because LSFL_RUNNING was set everything
+		 * else recovery hasn't started as well because ls_in_recovery
+		 * is still hold. So we should not run into the case that
+		 * resume_scan_timer() queues a timer that can occur in
+		 * a no op.
+		 */
+		resume_scan_timer(ls);
+		/* unblocks processes waiting to enter the dlm */
+		up_write(&ls->ls_in_recovery);
+		clear_bit(LSFL_RECOVER_LOCK, &ls->ls_flags);
+		error = 0;
+	}
+	spin_unlock_bh(&ls->ls_recover_lock);
+
+	write_unlock_bh(&ls->ls_recv_active);
+	return error;
+}
+
+static int ls_recover(struct dlm_ls *ls, struct dlm_recover *rv)
+{
+	LIST_HEAD(root_list);
+	unsigned long start;
+	int error, neg = 0;
+
+	log_rinfo(ls, "dlm_recover %llu", (unsigned long long)rv->seq);
+
+	mutex_lock(&ls->ls_recoverd_active);
+
+	dlm_callback_suspend(ls);
+
+	dlm_clear_inactive(ls);
+
+	/*
+	 * This list of root rsb's will be the basis of most of the recovery
+	 * routines.
+	 */
+
+	dlm_create_root_list(ls, &root_list);
+
+	/*
+	 * Add or remove nodes from the lockspace's ls_nodes list.
+	 *
+	 * Due to the fact that we must report all membership changes to lsops
+	 * or midcomms layer, it is not permitted to abort ls_recover() until
+	 * this is done.
+	 */
+
+	error = dlm_recover_members(ls, rv, &neg);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_members error %d", error);
+		goto fail_root_list;
+	}
+
+	dlm_recover_dir_nodeid(ls, &root_list);
+
+	/* Create a snapshot of all active rsbs were we are the master of.
+	 * During the barrier between dlm_recover_members_wait() and
+	 * dlm_recover_directory() other nodes can dump their necessary
+	 * directory dlm_rsb (r->res_dir_nodeid == nodeid) in rcom
+	 * communication dlm_copy_master_names() handling.
+	 *
+	 * TODO We should create a per lockspace list that contains rsbs
+	 * that we are the master of. Instead of creating this list while
+	 * recovery we keep track of those rsbs while locking handling and
+	 * recovery can use it when necessary.
+	 */
+	error = dlm_create_masters_list(ls);
+	if (error) {
+		log_rinfo(ls, "dlm_create_masters_list error %d", error);
+		goto fail_root_list;
+	}
+
+	ls->ls_recover_locks_in = 0;
+
+	dlm_set_recover_status(ls, DLM_RS_NODES);
+
+	error = dlm_recover_members_wait(ls, rv->seq);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_members_wait error %d", error);
+		dlm_release_masters_list(ls);
+		goto fail_root_list;
+	}
+
+	start = jiffies;
+
+	/*
+	 * Rebuild our own share of the directory by collecting from all other
+	 * nodes their master rsb names that hash to us.
+	 */
+
+	error = dlm_recover_directory(ls, rv->seq);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_directory error %d", error);
+		dlm_release_masters_list(ls);
+		goto fail_root_list;
+	}
+
+	dlm_set_recover_status(ls, DLM_RS_DIR);
+
+	error = dlm_recover_directory_wait(ls, rv->seq);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_directory_wait error %d", error);
+		dlm_release_masters_list(ls);
+		goto fail_root_list;
+	}
+
+	dlm_release_masters_list(ls);
+
+	/*
+	 * We may have outstanding operations that are waiting for a reply from
+	 * a failed node.  Mark these to be resent after recovery.  Unlock and
+	 * cancel ops can just be completed.
+	 */
+
+	dlm_recover_waiters_pre(ls);
+
+	if (dlm_recovery_stopped(ls)) {
+		error = -EINTR;
+		goto fail_root_list;
+	}
+
+	if (neg || dlm_no_directory(ls)) {
+		/*
+		 * Clear lkb's for departed nodes.
+		 */
+
+		dlm_recover_purge(ls, &root_list);
+
+		/*
+		 * Get new master nodeid's for rsb's that were mastered on
+		 * departed nodes.
+		 */
+
+		error = dlm_recover_masters(ls, rv->seq, &root_list);
+		if (error) {
+			log_rinfo(ls, "dlm_recover_masters error %d", error);
+			goto fail_root_list;
+		}
+
+		/*
+		 * Send our locks on remastered rsb's to the new masters.
+		 */
+
+		error = dlm_recover_locks(ls, rv->seq, &root_list);
+		if (error) {
+			log_rinfo(ls, "dlm_recover_locks error %d", error);
+			goto fail_root_list;
+		}
+
+		dlm_set_recover_status(ls, DLM_RS_LOCKS);
+
+		error = dlm_recover_locks_wait(ls, rv->seq);
+		if (error) {
+			log_rinfo(ls, "dlm_recover_locks_wait error %d", error);
+			goto fail_root_list;
+		}
+
+		log_rinfo(ls, "dlm_recover_locks %u in",
+			  ls->ls_recover_locks_in);
+
+		/*
+		 * Finalize state in master rsb's now that all locks can be
+		 * checked.  This includes conversion resolution and lvb
+		 * settings.
+		 */
+
+		dlm_recover_rsbs(ls, &root_list);
+	} else {
+		/*
+		 * Other lockspace members may be going through the "neg" steps
+		 * while also adding us to the lockspace, in which case they'll
+		 * be doing the recover_locks (RS_LOCKS) barrier.
+		 */
+		dlm_set_recover_status(ls, DLM_RS_LOCKS);
+
+		error = dlm_recover_locks_wait(ls, rv->seq);
+		if (error) {
+			log_rinfo(ls, "dlm_recover_locks_wait error %d", error);
+			goto fail_root_list;
+		}
+	}
+
+	dlm_release_root_list(&root_list);
+
+	/*
+	 * Purge directory-related requests that are saved in requestqueue.
+	 * All dir requests from before recovery are invalid now due to the dir
+	 * rebuild and will be resent by the requesting nodes.
+	 */
+
+	dlm_purge_requestqueue(ls);
+
+	dlm_set_recover_status(ls, DLM_RS_DONE);
+
+	error = dlm_recover_done_wait(ls, rv->seq);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_done_wait error %d", error);
+		goto fail;
+	}
+
+	dlm_clear_members_gone(ls);
+
+	dlm_callback_resume(ls);
+
+	error = enable_locking(ls, rv->seq);
+	if (error) {
+		log_rinfo(ls, "enable_locking error %d", error);
+		goto fail;
+	}
+
+	error = dlm_process_requestqueue(ls);
+	if (error) {
+		log_rinfo(ls, "dlm_process_requestqueue error %d", error);
+		goto fail;
+	}
+
+	error = dlm_recover_waiters_post(ls);
+	if (error) {
+		log_rinfo(ls, "dlm_recover_waiters_post error %d", error);
+		goto fail;
+	}
+
+	dlm_recover_grant(ls);
+
+	log_rinfo(ls, "dlm_recover %llu generation %u done: %u ms",
+		  (unsigned long long)rv->seq, ls->ls_generation,
+		  jiffies_to_msecs(jiffies - start));
+	mutex_unlock(&ls->ls_recoverd_active);
+
+	return 0;
+
+ fail_root_list:
+	dlm_release_root_list(&root_list);
+ fail:
+	mutex_unlock(&ls->ls_recoverd_active);
+
+	return error;
+}
+
+/* The dlm_ls_start() that created the rv we take here may already have been
+   stopped via dlm_ls_stop(); in that case we need to leave the RECOVERY_STOP
+   flag set. */
+
+static void do_ls_recovery(struct dlm_ls *ls)
+{
+	struct dlm_recover *rv = NULL;
+	int error;
+
+	spin_lock_bh(&ls->ls_recover_lock);
+	rv = ls->ls_recover_args;
+	ls->ls_recover_args = NULL;
+	if (rv && ls->ls_recover_seq == rv->seq)
+		clear_bit(LSFL_RECOVER_STOP, &ls->ls_flags);
+	spin_unlock_bh(&ls->ls_recover_lock);
+
+	if (rv) {
+		error = ls_recover(ls, rv);
+		switch (error) {
+		case 0:
+			ls->ls_recovery_result = 0;
+			complete(&ls->ls_recovery_done);
+
+			dlm_lsop_recover_done(ls);
+			break;
+		case -EINTR:
+			/* if recovery was interrupted -EINTR we wait for the next
+			 * ls_recover() iteration until it hopefully succeeds.
+			 */
+			log_rinfo(ls, "%s %llu interrupted and should be queued to run again",
+				  __func__, (unsigned long long)rv->seq);
+			break;
+		default:
+			log_rinfo(ls, "%s %llu error %d", __func__,
+				  (unsigned long long)rv->seq, error);
+
+			/* let new_lockspace() get aware of critical error */
+			ls->ls_recovery_result = error;
+			complete(&ls->ls_recovery_done);
+			break;
+		}
+
+		kfree(rv->nodes);
+		kfree(rv);
+	}
+}
+
+static int dlm_recoverd(void *arg)
+{
+	struct dlm_ls *ls;
+
+	ls = dlm_find_lockspace_local(arg);
+	if (!ls) {
+		log_print("dlm_recoverd: no lockspace %p", arg);
+		return -1;
+	}
+
+	down_write(&ls->ls_in_recovery);
+	set_bit(LSFL_RECOVER_LOCK, &ls->ls_flags);
+	wake_up(&ls->ls_recover_lock_wait);
+
+	while (1) {
+		/*
+		 * We call kthread_should_stop() after set_current_state().
+		 * This is because it works correctly if kthread_stop() is
+		 * called just before set_current_state().
+		 */
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (kthread_should_stop()) {
+			set_current_state(TASK_RUNNING);
+			break;
+		}
+		if (!test_bit(LSFL_RECOVER_WORK, &ls->ls_flags) &&
+		    !test_bit(LSFL_RECOVER_DOWN, &ls->ls_flags)) {
+			if (kthread_should_stop())
+				break;
+			schedule();
+		}
+		set_current_state(TASK_RUNNING);
+
+		if (test_and_clear_bit(LSFL_RECOVER_DOWN, &ls->ls_flags)) {
+			down_write(&ls->ls_in_recovery);
+			set_bit(LSFL_RECOVER_LOCK, &ls->ls_flags);
+			wake_up(&ls->ls_recover_lock_wait);
+		}
+
+		if (test_and_clear_bit(LSFL_RECOVER_WORK, &ls->ls_flags))
+			do_ls_recovery(ls);
+	}
+
+	if (test_bit(LSFL_RECOVER_LOCK, &ls->ls_flags))
+		up_write(&ls->ls_in_recovery);
+
+	dlm_put_lockspace(ls);
+	return 0;
+}
+
+int dlm_recoverd_start(struct dlm_ls *ls)
+{
+	struct task_struct *p;
+	int error = 0;
+
+	p = kthread_run(dlm_recoverd, ls, "dlm_recoverd");
+	if (IS_ERR(p))
+		error = PTR_ERR(p);
+	else
+                ls->ls_recoverd_task = p;
+	return error;
+}
+
+void dlm_recoverd_stop(struct dlm_ls *ls)
+{
+	kthread_stop(ls->ls_recoverd_task);
+}
+
+void dlm_recoverd_suspend(struct dlm_ls *ls)
+{
+	wake_up(&ls->ls_wait_general);
+	mutex_lock(&ls->ls_recoverd_active);
+}
+
+void dlm_recoverd_resume(struct dlm_ls *ls)
+{
+	mutex_unlock(&ls->ls_recoverd_active);
+}
+