Pull fuse update from Miklos Szeredi:

 - Allow some write requests to proceed in parallel

 - Fix a performance problem with allow_sys_admin_access

 - Add a special kind of invalidation that doesn't immediately purge
   submounts

 - On revalidation treat the target of rename(RENAME_NOREPLACE) the same
   as open(O_EXCL)

 - Use type safe helpers for some mnt_userns transformations

* tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Rearrange fuse_allow_current_process checks
  fuse: allow non-extending parallel direct writes on the same file
  fuse: remove the unneeded result variable
  fuse: port to vfs{g,u}id_t and associated helpers
  fuse: Remove user_ns check for FUSE_DEV_IOC_CLONE
  fuse: always revalidate rename target dentry
  fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY
  fs/fuse: Replace kmap() with kmap_local_page()

Pull setgid inheritance updates from Christian Brauner:
 "This contains the work to make setgid inheritance consistent between
  modifying a file and when changing ownership or mode as this has been
  a repeated source of very subtle bugs. The gist is that we perform the
  same permission checks in the write path as we do in the ownership and
  mode changing paths after this series where we're currently doing
  different things.

  We've already made setgid inheritance a lot more consistent and
  reliable in the last releases by moving setgid stripping from the
  individual filesystems up into the vfs. This aims to make the logic
  even more consistent and easier to understand and also to fix
  long-standing overlayfs setgid inheritance bugs. Miklos was nice
  enough to just let me carry the trivial overlayfs patches from Amir
  too.

  Below is a more detailed explanation how the current difference in
  setgid handling lead to very subtle bugs exemplified via overlayfs
  which is a victim of the current rules. I hope this explains why I
  think taking the regression risk here is worth it.

  A long while ago I found a few setgid inheritance bugs in overlayfs in
  the write path in certain conditions. Amir recently picked this back
  up in [1] and I jumped on board to fix this more generally.

  On the surface all that overlayfs would need to fix setgid inheritance
  would be to call file_remove_privs() or file_modified() but actually
  that isn't enough because the setgid inheritance api is wildly
  inconsistent in that area.

  Before this pr setgid stripping in file_remove_privs()'s old
  should_remove_suid() helper was inconsistent with other parts of the
  vfs. Specifically, it only raises ATTR_KILL_SGID if the inode is
  S_ISGID and S_IXGRP but not if the inode isn't in the caller's groups
  and the caller isn't privileged over the inode although we require
  this already in setattr_prepare() and setattr_copy() and so all
  filesystem implement this requirement implicitly because they have to
  use setattr_{prepare,copy}() anyway.

  But the inconsistency shows up in setgid stripping bugs for overlayfs
  in xfstests (e.g., generic/673, generic/683, generic/685, generic/686,
  generic/687). For example, we test whether suid and setgid stripping
  works correctly when performing various write-like operations as an
  unprivileged user (fallocate, reflink, write, etc.):

      echo "Test 1 - qa_user, non-exec file $verb"
      setup_testfile
      chmod a+rws $junk_file
      commit_and_check "$qa_user" "$verb" 64k 64k

  The test basically creates a file with 6666 permissions. While the
  file has the S_ISUID and S_ISGID bits set it does not have the S_IXGRP
  set.

  On a regular filesystem like xfs what will happen is:

      sys_fallocate()
      -> vfs_fallocate()
         -> xfs_file_fallocate()
            -> file_modified()
               -> __file_remove_privs()
                  -> dentry_needs_remove_privs()
                     -> should_remove_suid()
                  -> __remove_privs()
                     newattrs.ia_valid = ATTR_FORCE | kill;
                     -> notify_change()
                        -> setattr_copy()

  In should_remove_suid() we can see that ATTR_KILL_SUID is raised
  unconditionally because the file in the test has S_ISUID set.

  But we also see that ATTR_KILL_SGID won't be set because while the
  file is S_ISGID it is not S_IXGRP (see above) which is a condition for
  ATTR_KILL_SGID being raised.

  So by the time we call notify_change() we have attr->ia_valid set to
  ATTR_KILL_SUID | ATTR_FORCE.

  Now notify_change() sees that ATTR_KILL_SUID is set and does:

      ia_valid      = attr->ia_valid |= ATTR_MODE
      attr->ia_mode = (inode->i_mode & ~S_ISUID);

  which means that when we call setattr_copy() later we will definitely
  update inode->i_mode. Note that attr->ia_mode still contains S_ISGID.

  Now we call into the filesystem's ->setattr() inode operation which
  will end up calling setattr_copy(). Since ATTR_MODE is set we will
  hit:

      if (ia_valid & ATTR_MODE) {
              umode_t mode = attr->ia_mode;
              vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
              if (!vfsgid_in_group_p(vfsgid) &&
                  !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
                      mode &= ~S_ISGID;
              inode->i_mode = mode;
      }

  and since the caller in the test is neither capable nor in the group
  of the inode the S_ISGID bit is stripped.

  But assume the file isn't suid then ATTR_KILL_SUID won't be raised
  which has the consequence that neither the setgid nor the suid bits
  are stripped even though it should be stripped because the inode isn't
  in the caller's groups and the caller isn't privileged over the inode.

  If overlayfs is in the mix things become a bit more complicated and
  the bug shows up more clearly.

  When e.g., ovl_setattr() is hit from ovl_fallocate()'s call to
  file_remove_privs() then ATTR_KILL_SUID and ATTR_KILL_SGID might be
  raised but because the check in notify_change() is questioning the
  ATTR_KILL_SGID flag again by requiring S_IXGRP for it to be stripped
  the S_ISGID bit isn't removed even though it should be stripped:

      sys_fallocate()
      -> vfs_fallocate()
         -> ovl_fallocate()
            -> file_remove_privs()
               -> dentry_needs_remove_privs()
                  -> should_remove_suid()
               -> __remove_privs()
                  newattrs.ia_valid = ATTR_FORCE | kill;
                  -> notify_change()
                     -> ovl_setattr()
                        /* TAKE ON MOUNTER'S CREDS */
                        -> ovl_do_notify_change()
                           -> notify_change()
                        /* GIVE UP MOUNTER'S CREDS */
           /* TAKE ON MOUNTER'S CREDS */
           -> vfs_fallocate()
              -> xfs_file_fallocate()
                 -> file_modified()
                    -> __file_remove_privs()
                       -> dentry_needs_remove_privs()
                          -> should_remove_suid()
                       -> __remove_privs()
                          newattrs.ia_valid = attr_force | kill;
                          -> notify_change()

  The fix for all of this is to make file_remove_privs()'s
  should_remove_suid() helper perform the same checks as we already
  require in setattr_prepare() and setattr_copy() and have
  notify_change() not pointlessly requiring S_IXGRP again. It doesn't
  make any sense in the first place because the caller must calculate
  the flags via should_remove_suid() anyway which would raise
  ATTR_KILL_SGID

  Note that some xfstests will now fail as these patches will cause the
  setgid bit to be lost in certain conditions for unprivileged users
  modifying a setgid file when they would've been kept otherwise. I
  think this risk is worth taking and I explained and mentioned this
  multiple times on the list [2].

  Enforcing the rules consistently across write operations and
  chmod/chown will lead to losing the setgid bit in cases were it
  might've been retained before.

  While I've mentioned this a few times but it's worth repeating just to
  make sure that this is understood. For the sake of maintainability,
  consistency, and security this is a risk worth taking.

  If we really see regressions for workloads the fix is to have special
  setgid handling in the write path again with different semantics from
  chmod/chown and possibly additional duct tape for overlayfs. I'll
  update the relevant xfstests with if you should decide to merge this
  second setgid cleanup.

  Before that people should be aware that there might be failures for
  fstests where unprivileged users modify a setgid file"

Link: https://lore.kernel.org/linux-fsdevel/20221003123040.900827-1-amir73il@gmail.com [1]
Link: https://lore.kernel.org/linux-fsdevel/20221122142010.zchf2jz2oymx55qi@wittgenstein [2]

* tag 'fs.ovl.setgid.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
  fs: use consistent setgid checks in is_sxid()
  ovl: remove privs in ovl_fallocate()
  ovl: remove privs in ovl_copyfile()
  attr: use consistent sgid stripping checks
  attr: add setattr_should_drop_sgid()
  fs: move should_remove_suid()
  attr: add in_group_or_capable()

In general, as of now, in FUSE, direct writes on the same file are
serialized over inode lock i.e we hold inode lock for the full duration of
the write request.  I could not find in fuse code and git history a comment
which clearly explains why this exclusive lock is taken for direct writes.
Following might be the reasons for acquiring an exclusive lock but not be
limited to

 1) Our guess is some USER space fuse implementations might be relying on
    this lock for serialization.

 2) The lock protects against file read/write size races.

 3) Ruling out any issues arising from partial write failures.

This patch relaxes the exclusive lock for direct non-extending writes only.
File size extending writes might not need the lock either, but we are not
entirely sure if there is a risk to introduce any kind of regression.
Furthermore, benchmarking with fio does not show a difference between patch
versions that take on file size extension a) an exclusive lock and b) a
shared lock.

A possible example of an issue with i_size extending writes are write error
cases.  Some writes might succeed and others might fail for file system
internal reasons - for example ENOSPACE.  With parallel file size extending
writes it _might_ be difficult to revert the action of the failing write,
especially to restore the right i_size.

With these changes, we allow non-extending parallel direct writes on the
same file with the help of a flag called FOPEN_PARALLEL_DIRECT_WRITES.  If
this flag is set on the file (flag is passed from libfuse to fuse kernel as
part of file open/create), we do not take exclusive lock anymore, but
instead use a shared lock that allows non-extending writes to run in
parallel.  FUSE implementations which rely on this inode lock for
serialization can continue to do so and serialized direct writes are still
the default.  Implementations that do not do write serialization need to be
updated and need to set the FOPEN_PARALLEL_DIRECT_WRITES flag in their file
open/create reply.

On patch review there were concerns that network file systems (or vfs
multiple mounts of the same file system) might have issues with parallel
writes.  We believe this is not the case, as this is just a local lock,
which network file systems could not rely on anyway.  I.e. this lock is
just for local consistency.

Signed-off-by: Dharmendra Singh <dsingh@ddn.com>
Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

file_modified() must be called with inode lock held.  fuse_fallocate()
didn't lock the inode in case of just FALLOC_KEEP_SIZE flags value, which
resulted in a kernel Warning in notify_change().

Lock the inode unconditionally, like all other fallocate implementations
do.

Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Reported-and-tested-by: syzbot+462da39f0667b357c4b6@syzkaller.appspotmail.com
Fixes: 4a6f278d4827 ("fuse: add file_modified() to fallocate")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Add missing file_modified() call to fuse_file_fallocate().  Without this
fallocate on fuse failed to clear privileges.

Fixes: 05ba1f082300 ("fuse: add FALLOCATE operation")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Currently setgid stripping in file_remove_privs()'s should_remove_suid()
helper is inconsistent with other parts of the vfs. Specifically, it only
raises ATTR_KILL_SGID if the inode is S_ISGID and S_IXGRP but not if the
inode isn't in the caller's groups and the caller isn't privileged over the
inode although we require this already in setattr_prepare() and
setattr_copy() and so all filesystem implement this requirement implicitly
because they have to use setattr_{prepare,copy}() anyway.

But the inconsistency shows up in setgid stripping bugs for overlayfs in
xfstests (e.g., generic/673, generic/683, generic/685, generic/686,
generic/687). For example, we test whether suid and setgid stripping works
correctly when performing various write-like operations as an unprivileged
user (fallocate, reflink, write, etc.):

echo "Test 1 - qa_user, non-exec file $verb"
setup_testfile
chmod a+rws $junk_file
commit_and_check "$qa_user" "$verb" 64k 64k

The test basically creates a file with 6666 permissions. While the file has
the S_ISUID and S_ISGID bits set it does not have the S_IXGRP set. On a
regular filesystem like xfs what will happen is:

sys_fallocate()
-> vfs_fallocate()
   -> xfs_file_fallocate()
      -> file_modified()
         -> __file_remove_privs()
            -> dentry_needs_remove_privs()
               -> should_remove_suid()
            -> __remove_privs()
               newattrs.ia_valid = ATTR_FORCE | kill;
               -> notify_change()
                  -> setattr_copy()

In should_remove_suid() we can see that ATTR_KILL_SUID is raised
unconditionally because the file in the test has S_ISUID set.

But we also see that ATTR_KILL_SGID won't be set because while the file
is S_ISGID it is not S_IXGRP (see above) which is a condition for
ATTR_KILL_SGID being raised.

So by the time we call notify_change() we have attr->ia_valid set to
ATTR_KILL_SUID | ATTR_FORCE. Now notify_change() sees that
ATTR_KILL_SUID is set and does:

ia_valid = attr->ia_valid |= ATTR_MODE
attr->ia_mode = (inode->i_mode & ~S_ISUID);

which means that when we call setattr_copy() later we will definitely
update inode->i_mode. Note that attr->ia_mode still contains S_ISGID.

Now we call into the filesystem's ->setattr() inode operation which will
end up calling setattr_copy(). Since ATTR_MODE is set we will hit:

if (ia_valid & ATTR_MODE) {
        umode_t mode = attr->ia_mode;
        vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
        if (!vfsgid_in_group_p(vfsgid) &&
            !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
                mode &= ~S_ISGID;
        inode->i_mode = mode;
}

and since the caller in the test is neither capable nor in the group of the
inode the S_ISGID bit is stripped.

But assume the file isn't suid then ATTR_KILL_SUID won't be raised which
has the consequence that neither the setgid nor the suid bits are stripped
even though it should be stripped because the inode isn't in the caller's
groups and the caller isn't privileged over the inode.

If overlayfs is in the mix things become a bit more complicated and the bug
shows up more clearly. When e.g., ovl_setattr() is hit from
ovl_fallocate()'s call to file_remove_privs() then ATTR_KILL_SUID and
ATTR_KILL_SGID might be raised but because the check in notify_change() is
questioning the ATTR_KILL_SGID flag again by requiring S_IXGRP for it to be
stripped the S_ISGID bit isn't removed even though it should be stripped:

sys_fallocate()
-> vfs_fallocate()
   -> ovl_fallocate()
      -> file_remove_privs()
         -> dentry_needs_remove_privs()
            -> should_remove_suid()
         -> __remove_privs()
            newattrs.ia_valid = ATTR_FORCE | kill;
            -> notify_change()
               -> ovl_setattr()
                  // TAKE ON MOUNTER'S CREDS
                  -> ovl_do_notify_change()
                     -> notify_change()
                  // GIVE UP MOUNTER'S CREDS
     // TAKE ON MOUNTER'S CREDS
     -> vfs_fallocate()
        -> xfs_file_fallocate()
           -> file_modified()
              -> __file_remove_privs()
                 -> dentry_needs_remove_privs()
                    -> should_remove_suid()
                 -> __remove_privs()
                    newattrs.ia_valid = attr_force | kill;
                    -> notify_change()

The fix for all of this is to make file_remove_privs()'s
should_remove_suid() helper to perform the same checks as we already
require in setattr_prepare() and setattr_copy() and have notify_change()
not pointlessly requiring S_IXGRP again. It doesn't make any sense in the
first place because the caller must calculate the flags via
should_remove_suid() anyway which would raise ATTR_KILL_SGID.

While we're at it we move should_remove_suid() from inode.c to attr.c
where it belongs with the rest of the iattr helpers. Especially since it
returns ATTR_KILL_S{G,U}ID flags. We also rename it to
setattr_should_drop_suidgid() to better reflect that it indicates both
setuid and setgid bit removal and also that it returns attr flags.

Running xfstests with this doesn't report any regressions. We should really
try and use consistent checks.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

Pull more iov_iter updates from Al Viro:

 - more new_sync_{read,write}() speedups - ITER_UBUF introduction

 - ITER_PIPE cleanups

 - unification of iov_iter_get_pages/iov_iter_get_pages_alloc and
   switching them to advancing semantics

 - making ITER_PIPE take high-order pages without splitting them

 - handling copy_page_from_iter() for high-order pages properly

* tag 'pull-work.iov_iter-rebased' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (32 commits)
  fix copy_page_from_iter() for compound destinations
  hugetlbfs: copy_page_to_iter() can deal with compound pages
  copy_page_to_iter(): don't split high-order page in case of ITER_PIPE
  expand those iov_iter_advance()...
  pipe_get_pages(): switch to append_pipe()
  get rid of non-advancing variants
  ceph: switch the last caller of iov_iter_get_pages_alloc()
  9p: convert to advancing variant of iov_iter_get_pages_alloc()
  af_alg_make_sg(): switch to advancing variant of iov_iter_get_pages()
  iter_to_pipe(): switch to advancing variant of iov_iter_get_pages()
  block: convert to advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: saner helper for page array allocation
  fold __pipe_get_pages() into pipe_get_pages()
  ITER_XARRAY: don't open-code DIV_ROUND_UP()
  unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts
  unify xarray_get_pages() and xarray_get_pages_alloc()
  unify pipe_get_pages() and pipe_get_pages_alloc()
  iov_iter_get_pages(): sanity-check arguments
  iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper
  ...

Most of the users immediately follow successful iov_iter_get_pages()
with advancing by the amount it had returned.

Provide inline wrappers doing that, convert trivial open-coded
uses of those.

BTW, iov_iter_get_pages() never returns more than it had been asked
to; such checks in cifs ought to be removed someday...

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Equivalent of single-segment iovec.  Initialized by iov_iter_ubuf(),
checked for by iter_is_ubuf(), otherwise behaves like ITER_IOVEC
ones.

We are going to expose the things like ->write_iter() et.al. to those
in subsequent commits.

New predicate (user_backed_iter()) that is true for ITER_IOVEC and
ITER_UBUF; places like direct-IO handling should use that for
checking that pages we modify after getting them from iov_iter_get_pages()
would need to be dirtied.

DO NOT assume that replacing iter_is_iovec() with user_backed_iter()
will solve all problems - there's code that uses iter_is_iovec() to
decide how to poke around in iov_iter guts and for that the predicate
replacement obviously won't suffice.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull fuse updates from Miklos Szeredi:

 - Fix an issue with reusing the bdi in case of block based filesystems

 - Allow root (in init namespace) to access fuse filesystems in user
   namespaces if expicitly enabled with a module param

 - Misc fixes

* tag 'fuse-update-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: retire block-device-based superblock on force unmount
  vfs: function to prevent re-use of block-device-based superblocks
  virtio_fs: Modify format for virtio_fs_direct_access
  virtiofs: delete unused parameter for virtio_fs_cleanup_vqs
  fuse: Add module param for CAP_SYS_ADMIN access bypassing allow_other
  fuse: Remove the control interface for virtio-fs
  fuse: ioctl: translate ENOSYS
  fuse: limit nsec
  fuse: avoid unnecessary spinlock bump
  fuse: fix deadlock between atomic O_TRUNC and page invalidation
  fuse: write inode in fuse_release()