9front - general discussion about 9front
 help / color / mirror / Atom feed
From: Jacob Moody <moody@mail.posixcafe.org>
To: 9front@9front.org
Subject: Re: [9front] [PATCH] Unmount to remove sharp devices.
Date: Thu, 26 May 2022 18:33:25 -0600	[thread overview]
Message-ID: <3dd76207-af5a-eb0d-c56a-747ebe9965ad@posixcafe.org> (raw)
In-Reply-To: <F67CE959C225099FD668CDFF3114F377@smtp.pobox.com>

On 5/26/22 17:36, unobe@cpan.org wrote:
> Great work on this moody.  I have some (hopefully helpful) questions
> below.
> 
> 
> Quoth Jacob Moody <moody@mail.posixcafe.org>:
>> Another iteration.
>> To state all of what this does:
>>
>> A process can remove access to a driver through writing
>>
>> chdev [ 0! ] devmask
>>
>> to /dev/drivers. This is tied to the processes namegroup,
>> and is inherited on both RFCNAMEG and RFNAMEG. In order to provide
>> all the knobs RFNOMNT does, blocking 'M' is interpreted to block all mounting.
>>
>> Support for this new operation has been added to namespace files,
>> along with a matching chdev(1). /lib/namespace.ftp has been updated
>> to use chdev.
>> ...
>> --- /tmp/diff100000711164
>> +++ b/rc/bin/chdev
>> @@ -1,0 +1,3 @@
>> +#!/bin/rc
>> +
>> +echo chdev $* >> '#c/drivers'
>> ...
>> --- /tmp/diff100000711170
>> +++ b/sys/man/1/chdev
>> @@ -1,0 +1,93 @@
>> +.TH CHDEV 1
>> +.SH NAME
>> +chdev \- change kernel driver access
>> +.SH SYNOPSIS
>> +.B chdev
>> +[ 0! ] \f2devmask\fP...
> 
>> --- a/sys/src/9/port/dev.c
>> +++ b/sys/src/9/port/dev.c
>> @@ -31,6 +31,74 @@
>>  }
>>
>>  void
>> +devmask(Pgrp *pgrp, char *devs)
>> +{
>> +	int i, t, w;
>> +	int invert;
>> +	char *p;
>> +	Rune r;
>> +	u64int mask[nelem(pgrp->notallowed)];
>> +
>> +	
>> +	invert = 1;
>> +	switch(*devs){
>> +	case '!':
>> +		memset(mask, 0, sizeof mask);
>> +		devs++;
>> +		invert--;
>> +		break;
>> +	case '0':
>> +		devs = "";
>> +	default:
>> +		memset(mask, 0xFF, sizeof mask);
>> +		break;
>> +	}		
>> +
>> +	w = sizeof mask[0] * 8;
>> +	for(p = devs; *p != '\0';){
>> +		p += chartorune(&r, p);
>> +		t = devno(r, 1);
>> +		if(t == -1)
>> +			continue;
>> +		if(invert)
>> +			mask[t/w] &= ~(1<<t%w);
>> +		else
>> +			mask[t/w] |= 1<<t%w;
>> +	}
> 
> What happens if '!!!' is the prefix?  Should the '!' set invert = 0
> explicitly instead of invert--?  Does '!0' allow access to all
> drivers?
> 

That switch case is not looped over. We only check the very first character
for the prefix. The rest of the string is interpreted to be the driver string.
In both of your cases the prefix is '!' and the driver string only contains '0' or '!',
neither are real drivers so you block nothing.

  reply	other threads:[~2022-05-27  0:35 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-04 14:09 Jacob Moody
2022-05-04 15:05 ` ori
2022-05-04 15:31 ` ori
2022-05-04 16:15   ` Stanley Lieber
2022-05-04 17:41   ` Lyndon Nerenberg (VE7TFX/VE6BBM)
2022-05-04 17:55     ` Jacob Moody
2022-05-05  1:59       ` Alex Musolino
2022-05-05 16:07         ` Jacob Moody
2022-05-08  2:55           ` Jacob Moody
2022-05-11 14:47             ` Jacob Moody
2022-05-11 16:11               ` Stanley Lieber
2022-05-12  4:29                 ` Jacob Moody
2022-05-12  3:18             ` ori
2022-05-12  5:10               ` Jacob Moody
2022-05-12 14:21                 ` ori
2022-05-23  5:42                   ` Jacob Moody
2022-05-23 17:06                     ` cinap_lenrek
2022-05-23 17:37                       ` Jacob Moody
2022-05-25 19:03                         ` Jacob Moody
2022-05-25 20:53                           ` hiro
2022-05-25 21:20                             ` Jacob Moody
2022-05-26  5:55                               ` Jacob Moody
2022-05-26 23:36                                 ` unobe
2022-05-27  0:33                                   ` Jacob Moody [this message]
2022-05-27  3:25                                     ` unobe
2022-05-26  3:13                             ` ori
2022-05-27  1:11                           ` Lyndon Nerenberg (VE7TFX/VE6BBM)
2022-05-27  2:25                             ` Frank D. Engel, Jr.

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=3dd76207-af5a-eb0d-c56a-747ebe9965ad@posixcafe.org \
    --to=moody@mail.posixcafe.org \
    --cc=9front@9front.org \
    --subject='Re: [9front] [PATCH] Unmount to remove sharp devices.' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).