svn commit: r293227 - head/etc

[Devin Teske]

This e-mail is extremely hard to parse  and I think you are mistaken.

The -f flag is more than just a counter to a possible -i

Try to rm a file that has schg
You will get a prompt without -i
Adding -f will abate the prompt to attempt override of schg flag.

There are more conditions in rm that lead to a prompt than simply those conditions involving -i and adding -f abates them all.

-- 
Devin

> On Jan 5, 2016, at 6:48 PM, Bruce Evans <brde at optusnet.com.au> wrote:
> 
> On Tue, 5 Jan 2016, Ian Lepore wrote:
> 
>>> Log:
>>>  Use the more proper -f. Leave /bin/rm in place since that's what
>>>  other rc scripts have, though it isn't strictly necessary.
> 
> "proper -f" is hard to parse.  I think you mean:
> 
> Use 'rm -f' to turn off -i in case rm is broken and is an alias which
> has -i (and perhaps actually even something resembling rm) in it.  More
> precisely, use 'rm -f /usr/bin' to partly defend against the same bug
> in /bin/rm (where it would be larger).  Keep using /usr/rm instead of
> restoring the use of plain rm since that is what other rc scripts have.
> The previous change to use /bin/rm instead of plain rm was neither
> necessary nor sufficient for fixing the bug.  Neither is this one, but
> it gets closer.  It is a little-known bug in aliases that even absolute
> pathnames can be aliased.  So /bin/rm might be aliased to 'rm -ri /'.
> Appending -f would accidentally help for that too, by turning it into
> a syntax error, instead of accidentally making it more forceful by
> turning -ri into -rf.
> 
> Hopefully this is all FUD.  Non-interactive scripts shouldn't source any
> files that are not mentioned in the script.  /etc/rc depends on a secure
> environment being set up by init and probably gets it since init doesn't
> set up much.  sh(1) documents closing the security hole of sourcing the
> script in $ENV for non-interactive shells, but was never a problem for
> /etc/rc since init must be trusted to not put security holes in $ENV.
> But users could put security holes in a sourced config file like
> /etc/rc.conf.local.
> 
>>> Modified: head/etc/rc
>>> =====================================================================
>>> =========
>>> --- head/etc/rc    Tue Jan  5 21:20:46 2016    (r293226)
>>> +++ head/etc/rc    Tue Jan  5 21:20:47 2016    (r293227)
>>> @@ -132,9 +132,9 @@ done
>>> # Remove the firstboot sentinel, and reboot if it was requested.
>>> if [ -e ${firstboot_sentinel} ]; then
>>>    [ ${root_rw_mount} = "yes" ] || mount -uw /
>>> -    /bin/rm ${firstboot_sentinel}
>>> +    /bin/rm -f ${firstboot_sentinel}
>>>    if [ -e ${firstboot_sentinel}-reboot ]; then
>>> -        /bin/rm ${firstboot_sentinel}-reboot
>>> +        /bin/rm -f ${firstboot_sentinel}-reboot
>>>        [ ${root_rw_mount} = "yes" ] || mount -ur /
>>>        kill -INT 1
>>>    fi
>> 
>> Using rm -f to suppress an error message seems like a bad idea here --
>> if the sentinel file can't be removed that implies it's going to do
>> firstboot behavior every time it boots, and that's the sort of error
>> that should be in-your-face.  Especially on the reboot one because
>> you're going to be stuck in a reboot loop with no error message.
> 
> Er, -f on rm only turns off -i and supresses the warning message for
> failing to remove nonexistent files.  But we just tested that the file
> exists, and in the impossible even of a race making it not exist by
> the time that it runs, we have more problems than the failure of rm
> since we use the file's existence as a control for other things.
> 
> So the only effect of this -f is to turn off -i, which can only be set
> if the FUD was justified.
> 
> The correct fix seems to be 'unalias -a'.
> 
> Bruce
>