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, 153 insertions, 0 deletions

diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
new file mode 100644
index 000000000..0f731edde
--- /dev/null
+++ b/fs/notify/fdinfo.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/fsnotify_backend.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/inotify.h>
+#include <linux/fanotify.h>
+#include <linux/kernel.h>
+#include <linux/namei.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/seq_file.h>
+#include <linux/exportfs.h>
+
+#include "inotify/inotify.h"
+#include "fanotify/fanotify.h"
+#include "fdinfo.h"
+#include "fsnotify.h"
+#include "../internal.h"
+
+#if defined(CONFIG_PROC_FS)
+
+#if defined(CONFIG_INOTIFY_USER) || defined(CONFIG_FANOTIFY)
+
+static void show_fdinfo(struct seq_file *m, struct file *f,
+			void (*show)(struct seq_file *m,
+				     struct fsnotify_mark *mark))
+{
+	struct fsnotify_group *group = f->private_data;
+	struct fsnotify_mark *mark;
+
+	fsnotify_group_lock(group);
+	list_for_each_entry(mark, &group->marks_list, g_list) {
+		show(m, mark);
+		if (seq_has_overflowed(m))
+			break;
+	}
+	fsnotify_group_unlock(group);
+}
+
+#if defined(CONFIG_EXPORTFS)
+static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
+{
+	DEFINE_FLEX(struct file_handle, f, f_handle, handle_bytes, MAX_HANDLE_SZ);
+	int size, ret, i;
+
+	size = f->handle_bytes >> 2;
+
+	if (!super_trylock_shared(inode->i_sb))
+		return;
+
+	ret = exportfs_encode_fid(inode, (struct fid *)f->f_handle, &size);
+	up_read(&inode->i_sb->s_umount);
+
+	if ((ret == FILEID_INVALID) || (ret < 0))
+		return;
+
+	f->handle_type = ret;
+	f->handle_bytes = size * sizeof(u32);
+
+	seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:",
+		   f->handle_bytes, f->handle_type);
+
+	for (i = 0; i < f->handle_bytes; i++)
+		seq_printf(m, "%02x", (int)f->f_handle[i]);
+}
+#else
+static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
+{
+}
+#endif
+
+#ifdef CONFIG_INOTIFY_USER
+
+static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
+{
+	struct inotify_inode_mark *inode_mark;
+	struct inode *inode;
+
+	if (mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE)
+		return;
+
+	inode_mark = container_of(mark, struct inotify_inode_mark, fsn_mark);
+	inode = igrab(fsnotify_conn_inode(mark->connector));
+	if (inode) {
+		seq_printf(m, "inotify wd:%x ino:%llx sdev:%x mask:%x ignored_mask:0 ",
+			   inode_mark->wd, inode->i_ino, inode->i_sb->s_dev,
+			   inotify_mark_user_mask(mark));
+		show_mark_fhandle(m, inode);
+		seq_putc(m, '\n');
+		iput(inode);
+	}
+}
+
+void inotify_show_fdinfo(struct seq_file *m, struct file *f)
+{
+	show_fdinfo(m, f, inotify_fdinfo);
+}
+
+#endif /* CONFIG_INOTIFY_USER */
+
+#ifdef CONFIG_FANOTIFY
+
+static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
+{
+	unsigned int mflags = fanotify_mark_user_flags(mark);
+	struct inode *inode;
+
+	if (mark->connector->type == FSNOTIFY_OBJ_TYPE_INODE) {
+		inode = igrab(fsnotify_conn_inode(mark->connector));
+		if (!inode)
+			return;
+		seq_printf(m, "fanotify ino:%llx sdev:%x mflags:%x mask:%x ignored_mask:%x ",
+			   inode->i_ino, inode->i_sb->s_dev,
+			   mflags, mark->mask, mark->ignore_mask);
+		show_mark_fhandle(m, inode);
+		seq_putc(m, '\n');
+		iput(inode);
+	} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
+		struct mount *mnt = fsnotify_conn_mount(mark->connector);
+
+		seq_printf(m, "fanotify mnt_id:%x mflags:%x mask:%x ignored_mask:%x\n",
+			   mnt->mnt_id, mflags, mark->mask, mark->ignore_mask);
+	} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_SB) {
+		struct super_block *sb = fsnotify_conn_sb(mark->connector);
+
+		seq_printf(m, "fanotify sdev:%x mflags:%x mask:%x ignored_mask:%x\n",
+			   sb->s_dev, mflags, mark->mask, mark->ignore_mask);
+	} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_MNTNS) {
+		struct mnt_namespace *mnt_ns = fsnotify_conn_mntns(mark->connector);
+
+		seq_printf(m, "fanotify mnt_ns:%u mflags:%x mask:%x ignored_mask:%x\n",
+			   mnt_ns->ns.inum, mflags, mark->mask, mark->ignore_mask);
+	}
+}
+
+void fanotify_show_fdinfo(struct seq_file *m, struct file *f)
+{
+	struct fsnotify_group *group = f->private_data;
+
+	seq_printf(m, "fanotify flags:%x event-flags:%x\n",
+		   group->fanotify_data.flags & FANOTIFY_INIT_FLAGS,
+		   group->fanotify_data.f_flags);
+
+	show_fdinfo(m, f, fanotify_fdinfo);
+}
+
+#endif /* CONFIG_FANOTIFY */
+
+#endif /* CONFIG_INOTIFY_USER || CONFIG_FANOTIFY */
+
+#endif /* CONFIG_PROC_FS */