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, 36 insertions, 0 deletions

diff --git a/arch/riscv/lib/ashldi3.S b/arch/riscv/lib/ashldi3.S
new file mode 100644
index 000000000..c3408862e
--- /dev/null
+++ b/arch/riscv/lib/ashldi3.S
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/**
+ * Adopted for the Linux kernel from IPXE project, see
+ * https://github.com/ipxe/ipxe/blob/master/src/arch/riscv32/libgcc/llshift.S
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+/**
+ * Shift left
+ *
+ * @v a1:a0             Value to shift
+ * @v a2                Shift amount
+ * @ret a1:a0           Shifted value
+ */
+
+SYM_FUNC_START(__ashldi3)
+
+        /* Perform shift by 32 bits, if applicable */
+        li      t0, 32
+        sub     t1, t0, a2
+        bgtz    t1, 1f
+        mv      a1, a0
+        mv      a0, zero
+1:      /* Perform shift by modulo-32 bits, if applicable */
+        andi    a2, a2, 0x1f
+        beqz    a2, 2f
+        srl     t2, a0, t1
+        sll     a0, a0, a2
+        sll     a1, a1, a2
+        or      a1, a1, t2
+2:      ret
+
+SYM_FUNC_END(__ashldi3)
+EXPORT_SYMBOL(__ashldi3)