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, 41 insertions, 0 deletions

diff --git a/scripts/atomic/atomics.tbl b/scripts/atomic/atomics.tbl
new file mode 100644
index 000000000..903946cbf
--- /dev/null
+++ b/scripts/atomic/atomics.tbl
@@ -0,0 +1,41 @@
+# name	meta	args...
+#
+# Where meta contains a string of variants to generate.
+# Upper-case implies _{acquire,release,relaxed} variants.
+# Valid meta values are:
+# * B/b	- bool: returns bool
+# * v	- void: returns void
+# * I/i	- int: returns base type
+# * R	- return: returns base type (has _return variants)
+# * F/f	- fetch: returns base type (has fetch_ variants)
+# * l	- load: returns base type (has _acquire order variant)
+# * s	- store: returns void (has _release order variant)
+#
+# Where args contains list of type[:name], where type is:
+# * cv	- const pointer to atomic base type (atomic_t/atomic64_t/atomic_long_t)
+# * v	- pointer to atomic base type (atomic_t/atomic64_t/atomic_long_t)
+# * i	- base type (int/s64/long)
+# * p	- pointer to base type (int/s64/long)
+#
+read			l	cv
+set			s	v	i
+add			vRF	i	v
+sub			vRF	i	v
+inc			vRF	v
+dec			vRF	v
+and			vF	i	v
+andnot			vF	i	v
+or			vF	i	v
+xor			vF	i	v
+xchg			I	v	i:new
+cmpxchg			I	v	i:old	i:new
+try_cmpxchg		B	v	p:old	i:new
+sub_and_test		b	i	v
+dec_and_test		b	v
+inc_and_test		b	v
+add_negative		B	i	v
+add_unless		fb	v	i:a	i:u
+inc_not_zero		b	v
+inc_unless_negative	b	v
+dec_unless_positive	b	v
+dec_if_positive		i	v