Brian Norris b8de524ce4 debugfs: Only clobber mode/uid/gid on remount if asked
Users may have explicitly configured their debugfs permissions; we
shouldn't overwrite those just because a second mount appeared.

Only clobber if the options were provided at mount time.

Existing behavior:

  ## Pre-existing status: debugfs is 0755.
  # chmod 755 /sys/kernel/debug/
  # stat -c '%A' /sys/kernel/debug/
  drwxr-xr-x

  ## New mount sets kernel-default permissions:
  # mount -t debugfs none /mnt/foo
  # stat -c '%A' /mnt/foo
  drwx------

  ## Unexpected: the original mount changed permissions:
  # stat -c '%A' /sys/kernel/debug
  drwx------

New behavior:

  ## Pre-existing status: debugfs is 0755.
  # chmod 755 /sys/kernel/debug/
  # stat -c '%A' /sys/kernel/debug/
  drwxr-xr-x

  ## New mount inherits existing permissions:
  # mount -t debugfs none /mnt/foo
  # stat -c '%A' /mnt/foo
  drwxr-xr-x

  ## Expected: old mount is unchanged:
  # stat -c '%A' /sys/kernel/debug
  drwxr-xr-x

Full test cases are being submitted to LTP.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Link: https://lore.kernel.org/r/20220912163042.v3.1.Icbd40fce59f55ad74b80e5d435ea233579348a78@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-09-24 14:01:37 +02:00
2022-09-12 16:51:22 +02:00
2022-09-18 13:44:14 -07:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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