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, 177 insertions, 0 deletions

diff --git a/fs/nfsd/xdr.h b/fs/nfsd/xdr.h
new file mode 100644
index 000000000..852f71580
--- /dev/null
+++ b/fs/nfsd/xdr.h
@@ -0,0 +1,177 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* XDR types for nfsd. This is mainly a typing exercise. */
+
+#ifndef LINUX_NFSD_H
+#define LINUX_NFSD_H
+
+#include <linux/vfs.h>
+#include "nfsd.h"
+#include "nfsfh.h"
+
+struct nfsd_fhandle {
+	struct svc_fh		fh;
+};
+
+struct nfsd_sattrargs {
+	struct svc_fh		fh;
+	struct iattr		attrs;
+};
+
+struct nfsd_diropargs {
+	struct svc_fh		fh;
+	char *			name;
+	unsigned int		len;
+};
+
+struct nfsd_readargs {
+	struct svc_fh		fh;
+	__u32			offset;
+	__u32			count;
+};
+
+struct nfsd_writeargs {
+	svc_fh			fh;
+	__u32			offset;
+	__u32			len;
+	struct xdr_buf		payload;
+};
+
+struct nfsd_createargs {
+	struct svc_fh		fh;
+	char *			name;
+	unsigned int		len;
+	struct iattr		attrs;
+};
+
+struct nfsd_renameargs {
+	struct svc_fh		ffh;
+	char *			fname;
+	unsigned int		flen;
+	struct svc_fh		tfh;
+	char *			tname;
+	unsigned int		tlen;
+};
+
+struct nfsd_linkargs {
+	struct svc_fh		ffh;
+	struct svc_fh		tfh;
+	char *			tname;
+	unsigned int		tlen;
+};
+
+struct nfsd_symlinkargs {
+	struct svc_fh		ffh;
+	char *			fname;
+	unsigned int		flen;
+	char *			tname;
+	unsigned int		tlen;
+	struct iattr		attrs;
+	struct kvec		first;
+};
+
+struct nfsd_readdirargs {
+	struct svc_fh		fh;
+	__u32			cookie;
+	__u32			count;
+};
+
+struct nfsd_stat {
+	__be32			status;
+};
+
+struct nfsd_attrstat {
+	__be32			status;
+	struct svc_fh		fh;
+	struct kstat		stat;
+};
+
+struct nfsd_diropres  {
+	__be32			status;
+	struct svc_fh		fh;
+	struct kstat		stat;
+};
+
+struct nfsd_readlinkres {
+	__be32			status;
+	int			len;
+	struct page		*page;
+};
+
+struct nfsd_readres {
+	__be32			status;
+	struct svc_fh		fh;
+	unsigned long		count;
+	struct kstat		stat;
+	struct page		**pages;
+};
+
+struct nfsd_readdirres {
+	/* Components of the reply */
+	__be32			status;
+
+	int			count;
+
+	/* Used to encode the reply's entry list */
+	struct xdr_stream	xdr;
+	struct xdr_buf		dirlist;
+	struct readdir_cd	common;
+	unsigned int		cookie_offset;
+};
+
+struct nfsd_statfsres {
+	__be32			status;
+	struct kstatfs		stats;
+};
+
+/*
+ * Storage requirements for XDR arguments and results.
+ */
+union nfsd_xdrstore {
+	struct nfsd_sattrargs	sattr;
+	struct nfsd_diropargs	dirop;
+	struct nfsd_readargs	read;
+	struct nfsd_writeargs	write;
+	struct nfsd_createargs	create;
+	struct nfsd_renameargs	rename;
+	struct nfsd_linkargs	link;
+	struct nfsd_symlinkargs	symlink;
+	struct nfsd_readdirargs	readdir;
+};
+
+#define NFS2_SVC_XDRSIZE	sizeof(union nfsd_xdrstore)
+
+
+bool nfssvc_decode_fhandleargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_sattrargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_diropargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_readargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_writeargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_createargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_renameargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_linkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_symlinkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_decode_readdirargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+
+bool nfssvc_encode_statres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_attrstatres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_diropres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_readlinkres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_readres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_statfsres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+bool nfssvc_encode_readdirres(struct svc_rqst *rqstp, struct xdr_stream *xdr);
+
+void nfssvc_encode_nfscookie(struct nfsd_readdirres *resp, u32 offset);
+int nfssvc_encode_entry(void *data, const char *name, int namlen,
+			loff_t offset, u64 ino, unsigned int d_type);
+
+void nfssvc_release_attrstat(struct svc_rqst *rqstp);
+void nfssvc_release_diropres(struct svc_rqst *rqstp);
+void nfssvc_release_readres(struct svc_rqst *rqstp);
+
+/* Helper functions for NFSv2 ACL code */
+bool svcxdr_decode_fhandle(struct xdr_stream *xdr, struct svc_fh *fhp);
+bool svcxdr_encode_stat(struct xdr_stream *xdr, __be32 status);
+bool svcxdr_encode_fattr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
+			 const struct svc_fh *fhp, const struct kstat *stat);
+
+#endif /* LINUX_NFSD_H */