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, 17 insertions, 0 deletions

diff --git a/fs/hpfs/Kconfig b/fs/hpfs/Kconfig
new file mode 100644
index 000000000..ac1e9318e
--- /dev/null
+++ b/fs/hpfs/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config HPFS_FS
+	tristate "OS/2 HPFS file system support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	select FS_IOMAP
+	help
+	  OS/2 is IBM's operating system for PC's, the same as Warp, and HPFS
+	  is the file system used for organizing files on OS/2 hard disk
+	  partitions. Say Y if you want to be able to read files from and
+	  write files to an OS/2 HPFS partition on your hard drive. OS/2
+	  floppies however are in regular MSDOS format, so you don't need this
+	  option in order to be able to read them. Read
+	  <file:Documentation/filesystems/hpfs.rst>.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called hpfs.  If unsure, say N.