svn commit: r240770 - in head/usr.sbin/bsdconfig: . console mouse networking networking/share share startup startup/share timezone/share usermgmt/share

[Devin Teske]

On Sep 21, 2012, at 4:36 AM, Jilles Tjoelker wrote:

> On Fri, Sep 21, 2012 at 01:36:20AM +0000, Devin Teske wrote:
>> Author: dteske
>> Date: Fri Sep 21 01:36:20 2012
>> New Revision: 240770
>> URL: http://svn.freebsd.org/changeset/base/240770
> 
>> Log:
>>  Replace redirections to /dev/null with "close file-descriptor" syntax (>&-).
> 
>>  Reviewed by:	adrian (co-mentor)
>>  Approved by:	adrian (co-mentor)
> 
>> [snip]
> 
>> Modified: head/usr.sbin/bsdconfig/bsdconfig
>> ==============================================================================
>> --- head/usr.sbin/bsdconfig/bsdconfig	Fri Sep 21 00:36:35 2012	(r240769)
>> +++ head/usr.sbin/bsdconfig/bsdconfig	Fri Sep 21 01:36:20 2012	(r240770)
>> @@ -73,7 +73,7 @@ usage()
>> 	# Determine the maximum width of terminal/console
>> 	#
>> 	local max_size max_width
>> -	max_size=$( stty size 2> /dev/null )
>> +	max_size=$( stty size 2>&- )
>> 	: ${max_size:="24 80"}
>> 	max_width="${max_size#*[$IFS]}"
>> 	f_dprintf "max_width=[$max_width]"
>> [snip]
> 
> This change is risky because it may cause error messages to be written
> to unexpected files. The first file the utility opens will be fd 2, and
> if something decides to write an error message to fd 2 it will try to
> write to that file.
> 
> For this reason, the kernel will automatically open /dev/null if you
> execute suid/sgid binaries with fd 0, 1 and/or 2 closed.
> 
> Particularly with fd 1 (>&-) there is another danger in that the output
> may fail with [EBADF] rather than being silently discarded. This may
> cause unexpected failures.
> 
> If the reason is that there may be no /dev/null, then you will have to
> change the environment such that there will be a /dev/null.
> 

Jilles and I discussed in IRC and he showed me how I can make /dev/null available in the embedded environment that this was needed for.

I'm going to make another revision that reverses the changes in SVN r240770 (this change).

Thanks Jilles!
-- 
Devin

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