Pull overlayfs fix from Amir Goldstein:
 "Fix a regression from this merge window"

* tag 'ovl-fixes-6.7-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs:
  ovl: fix dentry reference leak after changes to underlying layers

syzbot excercised the forbidden practice of moving the workdir under
lowerdir while overlayfs is mounted and tripped a dentry reference leak.

Fixes: c63e56a4a652 ("ovl: do not open/llseek lower file with upper sb_writers held")
Reported-and-tested-by: syzbot+8608bb4553edb8c78f41@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Pull vfs fixes from Christian Brauner:

 - Avoid calling back into LSMs from vfs_getattr_nosec() calls.

   IMA used to query inode properties accessing raw inode fields without
   dedicated helpers. That was finally fixed a few releases ago by
   forcing IMA to use vfs_getattr_nosec() helpers.

   The goal of the vfs_getattr_nosec() helper is to query for attributes
   without calling into the LSM layer which would be quite problematic
   because incredibly IMA is called from __fput()...

     __fput()
       -> ima_file_free()

   What it does is to call back into the filesystem to update the file's
   IMA xattr. Querying the inode without using vfs_getattr_nosec() meant
   that IMA didn't handle stacking filesystems such as overlayfs
   correctly. So the switch to vfs_getattr_nosec() is quite correct. But
   the switch to vfs_getattr_nosec() revealed another bug when used on
   stacking filesystems:

     __fput()
       -> ima_file_free()
          -> vfs_getattr_nosec()
             -> i_op->getattr::ovl_getattr()
                -> vfs_getattr()
                   -> i_op->getattr::$WHATEVER_UNDERLYING_FS_getattr()
                      -> security_inode_getattr() # calls back into LSMs

   Now, if that __fput() happens from task_work_run() of an exiting task
   current->fs and various other pointer could already be NULL. So
   anything in the LSM layer relying on that not being NULL would be
   quite surprised.

   Fix that by passing the information that this is a security request
   through to the stacking filesystem by adding a new internal
   ATT_GETATTR_NOSEC flag. Now the callchain becomes:

     __fput()
       -> ima_file_free()
          -> vfs_getattr_nosec()
             -> i_op->getattr::ovl_getattr()
                -> if (AT_GETATTR_NOSEC)
                          vfs_getattr_nosec()
                   else
                          vfs_getattr()
                   -> i_op->getattr::$WHATEVER_UNDERLYING_FS_getattr()

 - Fix a bug introduced with the iov_iter rework from last cycle.

   This broke /proc/kcore by copying too much and without the correct
   offset.

 - Add a missing NULL check when allocating the root inode in
   autofs_fill_super().

 - Fix stable writes for multi-device filesystems (xfs, btrfs etc) and
   the block device pseudo filesystem.

   Stable writes used to be a superblock flag only, making it a per
   filesystem property. Add an additional AS_STABLE_WRITES mapping flag
   to allow for fine-grained control.

 - Ensure that offset_iterate_dir() returns 0 after reaching the end of
   a directory so it adheres to getdents() convention.

* tag 'vfs-6.7-rc3.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  libfs: getdents() should return 0 after reaching EOD
  xfs: respect the stable writes flag on the RT device
  xfs: clean up FS_XFLAG_REALTIME handling in xfs_ioctl_setattr_xflags
  block: update the stable_writes flag in bdev_add
  filemap: add a per-mapping stable writes flag
  autofs: add: new_inode check in autofs_fill_super()
  iov_iter: fix copy_page_to_iter_nofault()
  fs: Pass AT_GETATTR_NOSEC flag to getattr interface function

When vfs_getattr_nosec() calls a filesystem's getattr interface function
then the 'nosec' should propagate into this function so that
vfs_getattr_nosec() can again be called from the filesystem's gettattr
rather than vfs_getattr(). The latter would add unnecessary security
checks that the initial vfs_getattr_nosec() call wanted to avoid.
Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass
with the new getattr_flags parameter to the getattr interface function.
In overlayfs and ecryptfs use this flag to determine which one of the
two functions to call.

In a recent code change introduced to IMA vfs_getattr_nosec() ended up
calling vfs_getattr() in overlayfs, which in turn called
security_inode_getattr() on an exiting process that did not have
current->fs set anymore, which then caused a kernel NULL pointer
dereference. With this change the call to security_inode_getattr() can
be avoided, thus avoiding the NULL pointer dereference.

Reported-by: <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com>
Fixes: db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Tyler Hicks <code@tyhicks.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Suggested-by: Christian Brauner <brauner@kernel.org>
Co-developed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Link: https://lore.kernel.org/r/20231002125733.1251467-1-stefanb@linux.vnet.ibm.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

On failure to parse parameters in ovl_parse_param_lowerdir(), it is
necessary to update ctx->nr with the correct nr before using
ovl_reset_lowerdirs() to release l->name.

Reported-and-tested-by: syzbot+26eedf3631650972f17c@syzkaller.appspotmail.com
Fixes: c835110b588a ("ovl: remove unused code in lowerdir param parsing")
Co-authored-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Remove misleading /** prefix from a regular comment.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311121628.byHp8tkv-lkp@intel.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Pull vfs fanotify fsid updates from Christian Brauner:
 "This work is part of the plan to enable fanotify to serve as a drop-in
  replacement for inotify. While inotify is availabe on all filesystems,
  fanotify currently isn't.

  In order to support fanotify on all filesystems two things are needed:

   (1) all filesystems need to support AT_HANDLE_FID

   (2) all filesystems need to report a non-zero f_fsid

  This contains (1) and allows filesystems to encode non-decodable file
  handlers for fanotify without implementing any exportfs operations by
  encoding a file id of type FILEID_INO64_GEN from i_ino and
  i_generation.

  Filesystems that want to opt out of encoding non-decodable file ids
  for fanotify that don't support NFS export can do so by providing an
  empty export_operations struct.

  This also partially addresses (2) by generating f_fsid for simple
  filesystems as well as freevxfs. Remaining filesystems will be dealt
  with by separate patches.

  Finally, this contains the patch from the current exportfs maintainers
  which moves exportfs under vfs with Chuck, Jeff, and Amir as
  maintainers and vfs.git as tree"

* tag 'vfs-6.7.fsid' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  MAINTAINERS: create an entry for exportfs
  fs: fix build error with CONFIG_EXPORTFS=m or not defined
  freevxfs: derive f_fsid from bdev->bd_dev
  fs: report f_fsid from s_dev for "simple" filesystems
  exportfs: support encoding non-decodeable file handles by default
  exportfs: define FILEID_INO64_GEN* file handle types
  exportfs: make ->encode_fh() a mandatory method for NFS export
  exportfs: add helpers to check if filesystem can encode/decode file handles

Pull overlayfs updates from Amir Goldstein:

 - Overlayfs aio cleanups and fixes

   Cleanups and minor fixes in preparation for factoring out of
   read/write passthrough code.

 - Overlayfs lock ordering changes

   Hold mnt_writers only throughout copy up instead of a long lived
   elevated refcount.

 - Add support for nesting overlayfs private xattrs

   There are cases where you want to use an overlayfs mount as a
   lowerdir for another overlayfs mount. For example, if the system
   rootfs is on overlayfs due to composefs, or to make it volatile (via
   tmpfs), then you cannot currently store a lowerdir on the rootfs,
   because the inner overlayfs will eat all the whiteouts and overlay
   xattrs. This means you can't e.g. store on the rootfs a prepared
   container image for use with overlayfs.

   This adds support for nesting of overlayfs mounts by escaping the
   problematic features and unescaping them when exposing to the
   overlayfs user.

 - Add new mount options for appending lowerdirs

* tag 'ovl-update-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs:
  ovl: add support for appending lowerdirs one by one
  ovl: refactor layer parsing helpers
  ovl: store and show the user provided lowerdir mount option
  ovl: remove unused code in lowerdir param parsing
  ovl: Add documentation on nesting of overlayfs mounts
  ovl: Add an alternative type of whiteout
  ovl: Support escaped overlay.* xattrs
  ovl: Add OVL_XATTR_TRUSTED/USER_PREFIX_LEN macros
  ovl: Move xattr support to new xattrs.c file
  ovl: do not encode lower fh with upper sb_writers held
  ovl: do not open/llseek lower file with upper sb_writers held
  ovl: reorder ovl_want_write() after ovl_inode_lock()
  ovl: split ovl_want_write() into two helpers
  ovl: add helper ovl_file_modified()
  ovl: protect copying of realinode attributes to ovl inode
  ovl: punt write aio completion to workqueue
  ovl: propagate IOCB_APPEND flag on writes to realfile
  ovl: use simpler function to convert iocb to rw flags

Pull integrity updates from Mimi Zohar:
 "Four integrity changes: two IMA-overlay updates, an integrity Kconfig
  cleanup, and a secondary keyring update"

* tag 'integrity-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
  ima: detect changes to the backing overlay file
  certs: Only allow certs signed by keys on the builtin keyring
  integrity: fix indentation of config attributes
  ima: annotate iint mutex to avoid lockdep false positive warnings

Commit 18b44bc5a672 ("ovl: Always reevaluate the file signature for
IMA") forced signature re-evaulation on every file access.

Instead of always re-evaluating the file's integrity, detect a change
to the backing file, by comparing the cached file metadata with the
backing file's metadata.  Verifying just the i_version has not changed
is insufficient.  In addition save and compare the i_ino and s_dev
as well.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Tested-by: Eric Snowberg <eric.snowberg@oracle.com>
Tested-by: Raul E Rangel <rrangel@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>