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, 34 insertions, 0 deletions

diff --git a/fs/quota/compat.h b/fs/quota/compat.h
new file mode 100644
index 000000000..ef7d1e12d
--- /dev/null
+++ b/fs/quota/compat.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compat.h>
+
+struct compat_if_dqblk {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			dqb_bsoftlimit;
+	compat_u64			dqb_curspace;
+	compat_u64			dqb_ihardlimit;
+	compat_u64			dqb_isoftlimit;
+	compat_u64			dqb_curinodes;
+	compat_u64			dqb_btime;
+	compat_u64			dqb_itime;
+	compat_uint_t			dqb_valid;
+};
+
+struct compat_fs_qfilestat {
+	compat_u64			dqb_bhardlimit;
+	compat_u64			qfs_nblks;
+	compat_uint_t			qfs_nextents;
+};
+
+struct compat_fs_quota_stat {
+	__s8				qs_version;
+	__u16				qs_flags;
+	__s8				qs_pad;
+	struct compat_fs_qfilestat	qs_uquota;
+	struct compat_fs_qfilestat	qs_gquota;
+	compat_uint_t			qs_incoredqs;
+	compat_int_t			qs_btimelimit;
+	compat_int_t			qs_itimelimit;
+	compat_int_t			qs_rtbtimelimit;
+	__u16				qs_bwarnlimit;
+	__u16				qs_iwarnlimit;
+};