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, 25 insertions, 0 deletions

diff --git a/arch/alpha/boot/bootloader.lds b/arch/alpha/boot/bootloader.lds
new file mode 100644
index 000000000..8cdff54c6
--- /dev/null
+++ b/arch/alpha/boot/bootloader.lds
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+OUTPUT_FORMAT("elf64-alpha")
+ENTRY(__start)
+printk = srm_printk;
+SECTIONS
+{
+  . = 0x20000000;
+  .text : { *(.text) }
+  _etext = .;
+  PROVIDE (etext = .);
+  .rodata : { *(.rodata) *(.rodata.*) }
+  .data : { *(.data) CONSTRUCTORS }
+  .got : { *(.got) }
+  .sdata : { *(.sdata) }
+  _edata = .;
+  PROVIDE (edata = .);
+  .sbss : { *(.sbss) *(.scommon) }
+  .bss : { *(.bss) *(COMMON) }
+  _end = . ;
+  PROVIDE (end = .);
+
+  .mdebug 0 : { *(.mdebug) }
+  .note 0 : { *(.note) }
+  .comment 0 : { *(.comment) }
+}