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SubjectRe: seccomp() SECCOMP_RET_KILL_PROCESS text for man page
On Sat, Nov 18, 2017 at 12:04 PM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Hi Kees,
>
> I came up with the following text (patch below) to describe the
> SECCOMP_RET_KILL_PROCESS action that you added in 4.14. Does it
> look okay?
>
> SECCOMP_RET_KILL_PROCESS (since Linux 4.14)
> This value results in immediate termination of the process,
> with a core dump. The system call is not executed. By
> contrast with SECCOMP_RET_KILL_THREAD below, all threads in
> the thread group are terminated. (For a discussion of
> thread groups, see the description of the CLONE_THREAD flag
> in clone(2).)
>
> The process terminates as though killed by a SIGSYS signal.
> Even if a signal handler has been registered for SIGSYS,
> the handler will be ignored in this case and the process
> always terminates. To a parent process that is waiting on
> this process (using waitpid(2) or similar), the returned
> wstatus will indicate that its child was terminated as
> though by a SIGSYS signal.
>
> Cheers,
>
> Michael
>
>
> diff --git a/man2/seccomp.2 b/man2/seccomp.2
> index 2e912940e..1b6bb2e51 100644
> --- a/man2/seccomp.2
> +++ b/man2/seccomp.2
> @@ -399,6 +399,36 @@ returned by execution of all of the filters.
> In decreasing order of precedence,
> the values that may be returned by a seccomp filter are:
> .TP
> +.BR SECCOMP_RET_KILL_PROCESS " (since Linux 4.14)"
> +.\" commit 4d3b0b05aae9ee9ce0970dc4cc0fb3fad5e85945
> +.\" commit 0466bdb99e8744bc9befa8d62a317f0fd7fd7421
> +This value results in immediate termination of the process,
> +with a core dump.
> +The system call is not executed.
> +By contrast with
> +.BR SECCOMP_RET_KILL_THREAD
> +below, all threads in the thread group are terminated.
> +(For a discussion of thread groups, see the description of the
> +.BR CLONE_THREAD
> +flag in
> +.BR clone (2).)
> +.IP
> +The process terminates
> +.I "as though"
> +killed by a
> +.B SIGSYS
> +signal.
> +Even if a signal handler has been registered for
> +.BR SIGSYS ,
> +the handler will be ignored in this case and the process always terminates.
> +To a parent process that is waiting on this process (using
> +.BR waitpid (2)
> +or similar), the returned
> +.I wstatus
> +will indicate that its child was terminated as though by a
> +.BR SIGSYS
> +signal.
> +.TP
> .BR SECCOMP_RET_KILL_THREAD " (or " SECCOMP_RET_KILL )
> This value results in immediate termination of the thread
> that made the system call.

This is perfect, thank you!

One thing to adjust elsewhere would be to rename SECCOMP_RET_ACTION to
SECCOMP_RET_ACTION_FULL (the new mask covers the bits used by
SECCOMP_RET_KILL_PROCESS).

-Kees

>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/



--
Kees Cook
Pixel Security

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