** Changed in: linux (Ubuntu Bionic)
       Status: In Progress => Confirmed

** Changed in: linux (Ubuntu)
       Status: In Progress => Confirmed

** Changed in: linux (Ubuntu)
     Assignee: Joseph Salisbury (jsalisbury) => (unassigned)

** Changed in: linux (Ubuntu Bionic)
     Assignee: Joseph Salisbury (jsalisbury) => (unassigned)

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  Bug in selinux on ubuntu 16.04 with kernel 4.15.0-34

Status in linux package in Ubuntu:
Status in linux source package in Bionic:

Bug description:
  Hello, just found a bug in selinux.

  Whats going wrong:

  Copy a link with "-a" option while selinux is on.

  steps to reproduce:

  ~$ mkdir -p a/b
  ~$ ln -s b a/c
  ~$ cp -a a b
  cp: failed to restore the default file creation context: Invalid argument

  Results of my investigation:

  The "cp" of coreutils is calling "setfscreatecon (NULL)" to restore
  the default file creation context (coreutils-8.30/src/copy.c:1771) as
  it is stated in the selinux api

  As we see in the result of strace below, the kernel returns an -1 on
  try to restore the default file creation context. So in my opinion is
  the bug has to be in the selinux_setprocattr method in the
  security/selinux/hooks.c file.

  Part of "strace cp -a a b"

  lgetxattr("a/c", "security.selinux", "system_u:object_r:user_home_dir_t:s0", 
255) = 37
  readlink("a/c", "b", 2) = 1
  symlink("b", "b/a/c") = 0
  open("/proc/self/task/2136/attr/fscreate", O_RDWR|O_CLOEXEC) = 3
  write(3, NULL, 0) = -1 EINVAL (Invalid argument)
  close(3) = 0
  open("/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
  fstat(3, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0
  read(3, "# Locale name alias data base.\n#"..., 4096) = 2995
  read(3, "", 4096) = 0

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