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, 21 insertions, 0 deletions

diff --git a/fs/bfs/Kconfig b/fs/bfs/Kconfig
new file mode 100644
index 000000000..8e7ef866b
--- /dev/null
+++ b/fs/bfs/Kconfig
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config BFS_FS
+	tristate "BFS file system support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	help
+	  Boot File System (BFS) is a file system used under SCO UnixWare to
+	  allow the bootloader access to the kernel image and other important
+	  files during the boot process.  It is usually mounted under /stand
+	  and corresponds to the slice marked as "STAND" in the UnixWare
+	  partition.  You should say Y if you want to read or write the files
+	  on your /stand slice from within Linux.  You then also need to say Y
+	  to "UnixWare slices support", below.  More information about the BFS
+	  file system is contained in the file
+	  <file:Documentation/filesystems/bfs.rst>.
+
+	  If you don't know what this is about, say N.
+
+	  To compile this as a module, choose M here: the module will be called
+	  bfs.  Note that the file system of your root partition (the one
+	  containing the directory /) cannot be compiled as a module.