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The decision to log a seccomp action will always be subject to the value of the kernel.seccomp.actions_logged sysctl, even for processes that are being inspected via the audit subsystem, in an upcoming patch. Therefore, we need to emit an audit record on attempts at writing to the actions_logged sysctl when auditing is enabled. This patch updates the write handler for the actions_logged sysctl to emit an audit record on attempts to write to the sysctl. Successful writes to the sysctl will result in a record that includes a normalized list of logged actions in the "actions" field and a "res" field equal to 1. Unsuccessful writes to the sysctl will result in a record that doesn't include the "actions" field and has a "res" field equal to 0. Not all unsuccessful writes to the sysctl are audited. For example, an audit record will not be emitted if an unprivileged process attempts to open the sysctl file for reading since that access control check is not part of the sysctl's write handler. Below are some example audit records when writing various strings to the actions_logged sysctl. Writing "not-a-real-action", when the kernel.seccomp.actions_logged sysctl previously was "kill_process kill_thread trap errno trace log", emits this audit record: type=CONFIG_CHANGE msg=audit(1525392371.454:120): op=seccomp-logging actions=? old-actions=kill_process,kill_thread,trap,errno,trace,log res=0 If you then write "kill_process kill_thread errno trace log", this audit record is emitted: type=CONFIG_CHANGE msg=audit(1525392401.645:126): op=seccomp-logging actions=kill_process,kill_thread,errno,trace,log old-actions=kill_process,kill_thread,trap,errno,trace,log res=1 If you then write "log log errno trace kill_process kill_thread", which is unordered and contains the log action twice, it results in the same actions value as the previous record: type=CONFIG_CHANGE msg=audit(1525392436.354:132): op=seccomp-logging actions=kill_process,kill_thread,errno,trace,log old-actions=kill_process,kill_thread,errno,trace,log res=1 If you then write an empty string to the sysctl, this audit record is emitted: type=CONFIG_CHANGE msg=audit(1525392494.413:138): op=seccomp-logging actions=(none) old-actions=kill_process,kill_thread,errno,trace,log res=1 No audit records are generated when reading the actions_logged sysctl. Suggested-by: Steve Grubb <sgrubb@redhat.com> Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Paul Moore <paul@paul-moore.com>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.