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, 28 insertions, 0 deletions

diff --git a/fs/qnx6/Kconfig b/fs/qnx6/Kconfig
new file mode 100644
index 000000000..8e865d722
--- /dev/null
+++ b/fs/qnx6/Kconfig
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config QNX6FS_FS
+	tristate "QNX6 file system support (read only)"
+	depends on BLOCK && CRC32
+	select BUFFER_HEAD
+	help
+	  This is the file system used by the real-time operating systems
+	  QNX 6 (also called QNX RTP).
+	  Further information is available at <http://www.qnx.com/>.
+	  Say Y if you intend to mount QNX hard disks or floppies formatted
+          with a mkqnx6fs.
+	  However, keep in mind that this currently is a readonly driver!
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called qnx6.
+
+	  If you don't know whether you need it, then you don't need it:
+	  answer N.
+
+config QNX6FS_DEBUG
+	bool "QNX6 debugging information"
+	depends on QNX6FS_FS
+	help
+	  Turns on extended debugging output.
+
+	  If you are not a developer working on the QNX6FS, you probably don't
+	  want this:
+	  answer N.