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namespaces.7: Clarify details of sending signals to init from ancestor PID namespaces 

After email from Eric Biederman

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2013-01-23 04:29:52 +01:00
parent b16d757dfd
commit c0004fb480
1 changed files with 13 additions and 4 deletions
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man7/namespaces.7
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@ -353,14 +353,23 @@ can be sent to the "init" process by other members of the PID namespace.
This restriction applies even to privileged processes,
and prevents other members of the PID namespace from
accidentally killing the "init" process.
However, within ancestor namespaces
the "init" process is treated more like a normal user process:
any process can\(emsubject to the usual permission checks described in
Likewise, a process in an ancestor namespace
can\(emsubject to the usual permission checks described in
.BR kill (2)\(emsend
signals to the "init" process of a child PID namespace only
if the "init" process has established a handler for that signal.
(Within the handler, the
.I siginfo_t
.I si_pid
field described in
.BR sigaction (2)
will be zero.)
.B SIGKILL
or
.B SIGSTOP
to the "init" process.
are treated exceptionally:
these signals are forcibly delivered when sent from an ancestor PID namespace.
Neither of these signals can be caught by the "init" process,
and so will result in the usual actions associated with those signals
(respectively, terminating and stopping the process).