1. 14 Mar, 2018 5 commits
    • Bich HEMON's avatar
      dt-bindings: serial: stm32: add RS485 optional properties · 241672cb
      Bich HEMON authored
      Add options for enabling RS485 hardware control and configuring
      Driver Enable signal:
      - rs485-rts-delay
      - rs485-rx-during-tx
      - rs485-rts-active-low
      - linux,rs485-enabled-at-boot-time
      Signed-off-by: default avatarBich Hemon <bich.hemon@st.com>
      Reviewed-by: default avatarRob Herring <robh@kernel.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      241672cb
    • Christian Brauner's avatar
      selftests: add devpts selftests · ce290a19
      Christian Brauner authored
      This adds tests to check:
      - bind-mounts from /dev/pts/ptmx to /dev/ptmx work
      - non-standard mounts of devpts work
      - bind-mounts of /dev/pts/ptmx to locations that do not resolve to a valid
        slave pty path under the originating devpts mount fail
      Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
      Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      ce290a19
    • Christian Brauner's avatar
    • Christian Brauner's avatar
      devpts: resolve devpts bind-mounts · a319b01d
      Christian Brauner authored
      Most libcs will still look at /dev/ptmx when opening the master fd of a pty
      device. When /dev/ptmx is a bind-mount of /dev/pts/ptmx and the TIOCGPTPEER
      ioctl() is used to safely retrieve a file descriptor for the slave side of
      the pty based on the master fd, the /proc/self/fd/{0,1,2} symlinks will
      point to /. A very simply reproducer for this issue presupposing a libc
      that uses TIOCGPTPEER in its openpty() implementation is:
      
      unshare --mount
      mount --bind /dev/pts/ptmx /dev/ptmx
      chmod 666 /dev/ptmx
      script
      ls -al /proc/self/fd/0
      
      Having bind-mounts of /dev/pts/ptmx to /dev/ptmx not working correctly is a
      regression. In addition, it is also a fairly common scenario in containers
      employing user namespaces.
      
      The reason for the current failure is that the kernel tries to verify the
      useability of the devpts filesystem without resolving the /dev/ptmx
      bind-mount first. This will lead it to detect that the dentry is escaping
      its bind-mount. The reason is that while the devpts filesystem mounted at
      /dev/pts has the devtmpfs mounted at /dev as its parent mount:
      
      21 -- -- / /dev
      -- 21 -- / /dev/pts
      
      devtmpfs and devpts are on different devices
      
      -- -- 0:6  / /dev
      -- -- 0:20 / /dev/pts
      
      This has the consequence that the pathname of the parent directory of the
      devpts filesystem mount at /dev/pts is /. So if /dev/ptmx is a bind-mount
      of /dev/pts/ptmx then the /dev/ptmx bind-mount and the devpts mount at
      /dev/pts will end up being located on the same device which is recorded in
      the superblock of their vfsmount. This means the parent directory of the
      /dev/ptmx bind-mount will be /ptmx:
      
      -- -- ---- /ptmx /dev/ptmx
      
      Without the bind-mount resolution patch the kernel will now perform the
      bind-mount escape check directly on /dev/ptmx. The function responsible for
      this is devpts_ptmx_path() which calls pts_path() which in turn calls
      path_parent_directory(). Based on the above explanation,
      path_parent_directory() will yield / as the parent directory for the
      /dev/ptmx bind-mount and not the expected /dev. Thus, the kernel detects
      that /dev/ptmx is escaping its bind-mount and will set /proc/<pid>/fd/<nr>
      to /.
      
      This patch changes the logic to first resolve any bind-mounts. After the
      bind-mounts have been resolved (i.e. we have traced it back to the
      associated devpts mount) devpts_ptmx_path() can be called. In order to
      guarantee correct path generation for the slave file descriptor the kernel
      now requires that a pts directory is found in the parent directory of the
      ptmx bind-mount. This implies that when doing bind-mounts the ptmx
      bind-mount and the devpts mount should have a common parent directory. A
      valid example is:
      
      mount -t devpts devpts /dev/pts
      mount --bind /dev/pts/ptmx /dev/ptmx
      
      an invalid example is:
      
      mount -t devpts devpts /dev/pts
      mount --bind /dev/pts/ptmx /ptmx
      
      This allows us to support:
      - calling open on ptmx devices located inside non-standard devpts mounts:
        mount -t devpts devpts /mnt
        master = open("/mnt/ptmx", ...);
        slave = ioctl(master, TIOCGPTPEER, ...);
      - calling open on ptmx devices located outside the devpts mount with a
        common ancestor directory:
        mount -t devpts devpts /dev/pts
        mount --bind /dev/pts/ptmx /dev/ptmx
        master = open("/dev/ptmx", ...);
        slave = ioctl(master, TIOCGPTPEER, ...);
      
      while failing on ptmx devices located outside the devpts mount without a
      common ancestor directory:
        mount -t devpts devpts /dev/pts
        mount --bind /dev/pts/ptmx /ptmx
        master = open("/ptmx", ...);
        slave = ioctl(master, TIOCGPTPEER, ...);
      
      in which case save path generation cannot be guaranteed.
      Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
      Suggested-by: default avatarEric Biederman <ebiederm@xmission.com>
      Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Reviewed-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      a319b01d
    • Christian Brauner's avatar
      devpts: hoist out check for DEVPTS_SUPER_MAGIC · 7d71109d
      Christian Brauner authored
      Hoist the check whether we have already found a suitable devpts filesystem
      out of devpts_ptmx_path() in preparation for the devpts bind-mount
      resolution patch. This is a non-functional change.
      Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
      Reviewed-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      7d71109d
  2. 09 Mar, 2018 16 commits
  3. 28 Feb, 2018 19 commits