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Tetsuo Handa 0476fd4ff4 tomoyo: use realpath if symlink's pathname refers to procfs 
Fedora 41 has reached Linux 6.12 kernel with TOMOYO enabled. I observed
that /usr/lib/systemd/systemd executes /usr/lib/systemd/systemd-executor
by passing dirfd == 9 or dirfd == 16 upon execveat().

Commit ada1986d07 ("tomoyo: fallback to realpath if symlink's pathname
does not exist") used realpath only if symlink's pathname does not exist.
But an out of tree patch suggested that it will be reasonable to always
use realpath if symlink's pathname refers to proc filesystem.

Therefore, this patch changes the pathname used for checking "file execute"
and the domainname used after a successful execve() request.

Before:

  <kernel> /usr/lib/systemd/systemd
  file execute proc:/self/fd/16 exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor"
  file execute proc:/self/fd/9 exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor"

  <kernel> /usr/lib/systemd/systemd proc:/self/fd/16
  file execute /usr/sbin/auditd exec.realpath="/usr/sbin/auditd" exec.argv[0]="/usr/sbin/auditd"

  <kernel> /usr/lib/systemd/systemd proc:/self/fd/16 /usr/sbin/auditd

  <kernel> /usr/lib/systemd/systemd proc:/self/fd/9
  file execute /usr/bin/systemctl exec.realpath="/usr/bin/systemctl" exec.argv[0]="/usr/bin/systemctl"

  <kernel> /usr/lib/systemd/systemd proc:/self/fd/9 /usr/bin/systemctl

After:

  <kernel> /usr/lib/systemd/systemd
  file execute /usr/lib/systemd/systemd-executor exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor"

  <kernel> /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor
  file execute /usr/bin/systemctl exec.realpath="/usr/bin/systemctl" exec.argv[0]="/usr/bin/systemctl"
  file execute /usr/sbin/auditd exec.realpath="/usr/sbin/auditd" exec.argv[0]="/usr/sbin/auditd"

  <kernel> /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor /usr/bin/systemctl

  <kernel> /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor /usr/sbin/auditd

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
History 2024-12-17 19:03:39 +09:00
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README 

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 reStructuredText 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.