Add a function that checks is an extended attribute namespace is
supported for an inode, meaning that a handler must be present
for either the whole namespace, or at least one synthetic
xattr in the namespace.

To be used by the nfs server code when being queried for extended
attributes support.

Cc: linux-fsdevel@vger.kernel.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

set/removexattr on an exported filesystem should break NFS delegations.
This is true in general, but also for the upcoming support for
RFC 8726 (NFSv4 extended attribute support). Make sure that they do.

Additionally, they need to grow a _locked variant, since callers might
call this with i_rwsem held (like the NFS server code).

Cc: stable@vger.kernel.org # v4.9+
Cc: linux-fsdevel@vger.kernel.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

`removed_sized` isn't correctly initialized (as the doc comment
suggests) on memory allocation failures. Fix by moving initialization up
a bit.

Fixes: 0c47383ba3bd ("kernfs: Add option to enable user xattrs")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Tejun Heo <tj@kernel.org>

This helps set up size accounting in the next commit. Without this out
param, it's difficult to find out the removed xattr size without taking
a lock for longer and walking the xattr linked list twice.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

xattr values have a 64k maximum size. This can result in an order 4
kmalloc request which can be difficult to fulfill. Since xattrs do not
need physically contiguous memory, we can switch to kvmalloc and not
have to worry about higher order allocations failing.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 786534b92f3c introduced a regression that caused listxattr to
return the POSIX ACL attribute names even though sysfs doesn't support
POSIX ACLs.  This happens because simple_xattr_list checks for NULL
i_acl / i_default_acl, but inode_init_always initializes those fields
to ACL_NOT_CACHED ((void *)-1).  For example:
    $ getfattr -m- -d /sys
    /sys: system.posix_acl_access: Operation not supported
    /sys: system.posix_acl_default: Operation not supported
Fix this in simple_xattr_list by checking if the filesystem supports POSIX ACLs.

Fixes: 786534b92f3c ("tmpfs: listxattr should include POSIX ACL xattrs")
Reported-by:  Marc Aurèle La France <tsi@tuyoix.net>
Tested-by: Marc Aurèle La France <tsi@tuyoix.net>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull namespace fixes from Eric Biederman:
 "This is a set of four fairly obvious bug fixes:

   - a switch from d_find_alias to d_find_any_alias because the xattr
     code perversely takes a dentry

   - two mutex vs copy_to_user fixes from Jann Horn

   - a fix to use a sanitized size not the size userspace passed in from
     Christian Brauner"

* 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  getxattr: use correct xattr length
  sys: don't hold uts_sem while accessing userspace memory
  userns: move user access out of the mutex
  cap_inode_getsecurity: use d_find_any_alias() instead of d_find_alias()

When running in a container with a user namespace, if you call getxattr
with name = "system.posix_acl_access" and size % 8 != 4, then getxattr
silently skips the user namespace fixup that it normally does resulting in
un-fixed-up data being returned.
This is caused by posix_acl_fix_xattr_to_user() being passed the total
buffer size and not the actual size of the xattr as returned by
vfs_getxattr().
This commit passes the actual length of the xattr as returned by
vfs_getxattr() down.

A reproducer for the issue is:

  touch acl_posix

  setfacl -m user:0:rwx acl_posix

and the compile:

  #define _GNU_SOURCE
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/types.h>
  #include <unistd.h>
  #include <attr/xattr.h>

  /* Run in user namespace with nsuid 0 mapped to uid != 0 on the host. */
  int main(int argc, void **argv)
  {
          ssize_t ret1, ret2;
          char buf1[128], buf2[132];
          int fret = EXIT_SUCCESS;
          char *file;

          if (argc < 2) {
                  fprintf(stderr,
                          "Please specify a file with "
                          "\"system.posix_acl_access\" permissions set\n");
                  _exit(EXIT_FAILURE);
          }
          file = argv[1];

          ret1 = getxattr(file, "system.posix_acl_access",
                          buf1, sizeof(buf1));
          if (ret1 < 0) {
                  fprintf(stderr, "%s - Failed to retrieve "
                                  "\"system.posix_acl_access\" "
                                  "from \"%s\"\n", strerror(errno), file);
                  _exit(EXIT_FAILURE);
          }

          ret2 = getxattr(file, "system.posix_acl_access",
                          buf2, sizeof(buf2));
          if (ret2 < 0) {
                  fprintf(stderr, "%s - Failed to retrieve "
                                  "\"system.posix_acl_access\" "
                                  "from \"%s\"\n", strerror(errno), file);
                  _exit(EXIT_FAILURE);
          }

          if (ret1 != ret2) {
                  fprintf(stderr, "The value of \"system.posix_acl_"
                                  "access\" for file \"%s\" changed "
                                  "between two successive calls\n", file);
                  _exit(EXIT_FAILURE);
          }

          for (ssize_t i = 0; i < ret2; i++) {
                  if (buf1[i] == buf2[i])
                          continue;

                  fprintf(stderr,
                          "Unexpected different in byte %zd: "
                          "%02x != %02x\n", i, buf1[i], buf2[i]);
                  fret = EXIT_FAILURE;
          }

          if (fret == EXIT_SUCCESS)
                  fprintf(stderr, "Test passed\n");
          else
                  fprintf(stderr, "Test failed\n");

          _exit(fret);
  }
and run:

  ./tester acl_posix

On a non-fixed up kernel this should return something like:

  root@c1:/# ./t
  Unexpected different in byte 16: ffffffa0 != 00
  Unexpected different in byte 17: ffffff86 != 00
  Unexpected different in byte 18: 01 != 00

and on a fixed kernel:

  root@c1:~# ./t
  Test passed

Cc: stable@vger.kernel.org
Fixes: 2f6f0654ab61 ("userns: Convert vfs posix_acl support to use kuids and kgids")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=199945
Reported-by: Colin Watson <cjwatson@ubuntu.com>
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

This reverts commit 7c6893e3c9abf6a9676e060a1e35e5caca673d57.

Overlayfs no longer relies on the vfs for checking writability of files.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>