The reason is that in order to protect a process procctl(2) needs the PRIV_VM_MADV_PROTECT privilege, which is currently denied in jails (see kern_jail.c). MFC after: 1 week
140 lines
3.8 KiB
Groff
140 lines
3.8 KiB
Groff
.\" Copyright (c) 2013 Hudson River Trading LLC
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.\" Written by: John H. Baldwin <jhb@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 12, 2022
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.Dt PROTECT 1
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.Os
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.Sh NAME
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.Nm protect
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.Nd "protect processes from being killed when swap space is exhausted"
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.Sh SYNOPSIS
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.Nm
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.Op Fl i
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.Ar command
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.Nm
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.Op Fl cdi
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.Fl g Ar pgrp
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.Nm
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.Op Fl cdi
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.Fl p Ar pid
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.Sh DESCRIPTION
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The
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.Nm
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command is used to mark processes as protected.
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The kernel does not kill protected processes when swap space is exhausted.
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Note that this protected state is not inherited by child processes by default.
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.Pp
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The options are:
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.Bl -tag -width command
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.It Fl c
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Remove protection from the specified processes.
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.It Fl d
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Apply the operation to all current children of the specified processes.
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.It Fl i
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Apply the operation to all future children of the specified processes.
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.It Fl g Ar pgrp
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Apply the operation to all processes in the specified process group.
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.It Fl p Ar pid
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Apply the operation to the specified process.
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.It Ar command
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Execute
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.Ar command
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as a protected process.
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.El
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.Pp
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Note that only one of the
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.Fl p
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or
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.Fl g
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flags may be specified when adjusting the state of existing processes.
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.Pp
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Daemons can be protected on startup using
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.Ao Ar name Ac Ns Va _oomprotect
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option from
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.Xr rc.conf 5 .
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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Mark the Xorg server as protected:
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.Pp
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.Dl "pgrep Xorg | xargs protect -p"
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.Pp
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Protect all ssh sessions and their child processes:
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.Pp
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.Dl "pgrep sshd | xargs protect -dip"
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.Pp
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Remove protection from all current and future processes:
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.Pp
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.Dl "protect -cdi -p 1"
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.Pp
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Using
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.Xr ps 1
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to check if the protect flag has been applied to the process:
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.Pp
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.Dl "ps -O flags,flags2 -p 64430"
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.Pp
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.Dl " PID F F2 TT STAT TIME COMMAND"
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.Dl "64430 10104002 00000001 5 S+ 0:00.00 ./main"
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.Dl " ^P ^PI"
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.Pp
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In the above example
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.Nm P
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points at the protected flag and
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.Nm PI
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points at the inheritance flag.
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The process is protected if
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.Nm P
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bit is set to 1.
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All children of this process will also be protected if
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.Nm PI
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bit is set to 1.
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.Sh DIAGNOSTICS
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.Bl -diag
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.It "protect: procctl: Operation not permitted"
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The
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.Nm
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command does not have the required permissions to protect selected processes.
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There are many reasons why this could be the case, e.g.:
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.Bl -dash
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.It
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.Nm
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is not executed by root.
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.It
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.Nm
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is executed inside a
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.Xr jail 8 ,
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which is not supported at the moment.
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.El
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.El
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.Sh SEE ALSO
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.Xr ps 1 ,
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.Xr procctl 2 ,
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.Xr rc.conf 5
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.Sh BUGS
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If you protect a runaway process that allocates all memory the system will
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deadlock.
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