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, 68 insertions, 0 deletions

diff --git a/scripts/module.lds.S b/scripts/module.lds.S
new file mode 100644
index 000000000..b62683061
--- /dev/null
+++ b/scripts/module.lds.S
@@ -0,0 +1,68 @@
+/*
+ * Common module linker script, always used when linking a module.
+ * Archs are free to supply their own linker scripts.  ld will
+ * combine them automatically.
+ */
+#ifdef CONFIG_UNWIND_TABLES
+#define DISCARD_EH_FRAME
+#else
+#define DISCARD_EH_FRAME	*(.eh_frame)
+#endif
+
+#include <asm-generic/codetag.lds.h>
+
+SECTIONS {
+	/DISCARD/ : {
+		*(.discard)
+		*(.discard.*)
+		*(.export_symbol)
+		*(.no_trim_symbol)
+	}
+
+	__ksymtab		0 : ALIGN(8) { *(SORT(___ksymtab+*)) }
+	__kcrctab		0 : ALIGN(4) { *(SORT(___kcrctab+*)) }
+	__kflagstab		0 : ALIGN(1) { *(SORT(___kflagstab+*)) }
+
+	.ctors			0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
+	.init_array		0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
+
+	.altinstructions	0 : ALIGN(8) { KEEP(*(.altinstructions)) }
+	__bug_table		0 : ALIGN(8) { KEEP(*(__bug_table)) }
+	__jump_table		0 : ALIGN(8) { KEEP(*(__jump_table)) }
+	__ex_table		0 : ALIGN(4) { KEEP(*(__ex_table)) }
+
+	__patchable_function_entries 0 : { *(__patchable_function_entries) }
+
+	.init.klp_funcs		0 : ALIGN(8) { KEEP(*(.init.klp_funcs)) }
+	.init.klp_objects	0 : ALIGN(8) { KEEP(*(.init.klp_objects)) }
+
+#ifdef CONFIG_ARCH_USES_CFI_TRAPS
+	__kcfi_traps		0 : { KEEP(*(.kcfi_traps)) }
+#endif
+
+#ifndef CONFIG_ARCH_WANTS_MODULES_TEXT_SECTIONS
+	.text			0 : {
+		*(.text .text.[0-9a-zA-Z_]*)
+	}
+#endif
+
+	.bss			0 : {
+		*(.bss .bss.[0-9a-zA-Z_]*)
+		*(.bss..L*)
+	}
+
+	.data			0 : {
+		*(.data .data.[0-9a-zA-Z_]*)
+		*(.data..L*)
+	}
+
+	.rodata			0 : {
+		*(.rodata .rodata.[0-9a-zA-Z_]*)
+		*(.rodata..L*)
+	}
+
+	MOD_SEPARATE_CODETAG_SECTIONS()
+}
+
+/* bring in arch-specific sections */
+#include <asm/module.lds.h>