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, 128 insertions, 0 deletions

diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
new file mode 100644
index 000000000..734a45e51
--- /dev/null
+++ b/Documentation/filesystems/index.rst
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+.. _filesystems_index:
+
+===============================
+Filesystems in the Linux kernel
+===============================
+
+This under-development manual will, some glorious day, provide
+comprehensive information on how the Linux virtual filesystem (VFS) layer
+works, along with the filesystems that sit below it.  For now, what we have
+can be found below.
+
+Core VFS documentation
+======================
+
+See these manuals for documentation about the VFS layer itself and how its
+algorithms work.
+
+.. toctree::
+   :maxdepth: 2
+
+   vfs
+   path-lookup
+   api-summary
+   splice
+   locking
+   directory-locking
+   devpts
+   dnotify
+   fiemap
+   files
+   locks
+   mmap_prepare
+   multigrain-ts
+   mount_api
+   quota
+   seq_file
+   sharedsubtree
+   idmappings
+   iomap/index
+
+   automount-support
+
+   caching/index
+
+   porting
+   adding-new-filesystems
+
+Filesystem support layers
+=========================
+
+Documentation for the support code within the filesystem layer for use in
+filesystem implementations.
+
+.. toctree::
+   :maxdepth: 2
+
+   buffer
+   journalling
+   fscrypt
+   fsverity
+   netfs_library
+
+Filesystems
+===========
+
+Documentation for filesystem implementations.
+
+.. toctree::
+   :maxdepth: 2
+
+   9p
+   adfs
+   affs
+   afs
+   autofs
+   autofs-mount-control
+   befs
+   bfs
+   btrfs
+   ceph
+   coda
+   configfs
+   cramfs
+   dax
+   debugfs
+   dlmfs
+   ecryptfs
+   efivarfs
+   erofs
+   ext2
+   ext3
+   ext4/index
+   f2fs
+   failfs
+   gfs2/index
+   hfs
+   hfsplus
+   hpfs
+   fuse/index
+   inotify
+   isofs
+   nilfs2
+   nfs/index
+   ntfs
+   ntfs3
+   ocfs2
+   ocfs2-online-filecheck
+   omfs
+   orangefs
+   overlayfs
+   proc
+   qnx6
+   ramfs-rootfs-initramfs
+   relay
+   resctrl
+   romfs
+   smb/index
+   spufs/index
+   squashfs
+   sysfs
+   tmpfs
+   ubifs
+   ubifs-authentication
+   udf
+   virtiofs
+   vfat
+   xfs/index
+   zonefs