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, 106 insertions, 0 deletions

diff --git a/fs/smb/client/fscache.h b/fs/smb/client/fscache.h
new file mode 100644
index 000000000..352122288
--- /dev/null
+++ b/fs/smb/client/fscache.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: LGPL-2.1 */
+/*
+ *   CIFS filesystem cache interface definitions
+ *
+ *   Copyright (c) 2010 Novell, Inc.
+ *   Authors(s): Suresh Jayaraman (sjayaraman@suse.de>
+ *
+ */
+#ifndef _CIFS_FSCACHE_H
+#define _CIFS_FSCACHE_H
+
+#include <linux/swap.h>
+#include <linux/fscache.h>
+
+#include "cifsglob.h"
+
+/*
+ * Coherency data attached to CIFS volume within the cache
+ */
+struct cifs_fscache_volume_coherency_data {
+	__le64	resource_id;		/* unique server resource id */
+	__le64	vol_create_time;
+	__le32	vol_serial_number;
+} __packed;
+
+/*
+ * Coherency data attached to CIFS inode within the cache.
+ */
+struct cifs_fscache_inode_coherency_data {
+	__le64 last_write_time_sec;
+	__le64 last_change_time_sec;
+	__le32 last_write_time_nsec;
+	__le32 last_change_time_nsec;
+};
+
+#ifdef CONFIG_CIFS_FSCACHE
+
+/*
+ * fscache.c
+ */
+int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon);
+void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon);
+void cifs_fscache_get_inode_cookie(struct inode *inode);
+void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update);
+void cifs_fscache_release_inode_cookie(struct inode *inode);
+int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon);
+void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon);
+
+void cifs_fscache_get_inode_cookie(struct inode *inode);
+void cifs_fscache_release_inode_cookie(struct inode *inode);
+void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update);
+
+static inline
+void cifs_fscache_fill_coherency(struct inode *inode,
+				 struct cifs_fscache_inode_coherency_data *cd)
+{
+	struct timespec64 ctime = inode_get_ctime(inode);
+	struct timespec64 mtime = inode_get_mtime(inode);
+
+	memset(cd, 0, sizeof(*cd));
+	cd->last_write_time_sec   = cpu_to_le64(mtime.tv_sec);
+	cd->last_write_time_nsec  = cpu_to_le32(mtime.tv_nsec);
+	cd->last_change_time_sec  = cpu_to_le64(ctime.tv_sec);
+	cd->last_change_time_nsec = cpu_to_le32(ctime.tv_nsec);
+}
+
+
+static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode)
+{
+	return netfs_i_cookie(&CIFS_I(inode)->netfs);
+}
+
+static inline void cifs_invalidate_cache(struct inode *inode, unsigned int flags)
+{
+	struct cifs_fscache_inode_coherency_data cd;
+
+	cifs_fscache_fill_coherency(inode, &cd);
+	fscache_invalidate(cifs_inode_cookie(inode), &cd,
+			   i_size_read(inode), flags);
+}
+
+static inline bool cifs_fscache_enabled(struct inode *inode)
+{
+	return fscache_cookie_enabled(cifs_inode_cookie(inode));
+}
+
+#else /* CONFIG_CIFS_FSCACHE */
+static inline
+void cifs_fscache_fill_coherency(struct inode *inode,
+				 struct cifs_fscache_inode_coherency_data *cd)
+{
+}
+
+static inline int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon) { return 0; }
+static inline void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon) {}
+
+static inline void cifs_fscache_get_inode_cookie(struct inode *inode) {}
+static inline void cifs_fscache_release_inode_cookie(struct inode *inode) {}
+static inline void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update) {}
+static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode) { return NULL; }
+static inline void cifs_invalidate_cache(struct inode *inode, unsigned int flags) {}
+static inline bool cifs_fscache_enabled(struct inode *inode) { return false; }
+
+#endif /* CONFIG_CIFS_FSCACHE */
+
+#endif /* _CIFS_FSCACHE_H */