Date: Tue, 5 Jan 2016 19:16:32 -0800 From: Devin Teske <devin@shxd.cx> To: Bruce Evans <brde@optusnet.com.au> Cc: Ian Lepore <ian@freebsd.org>, Warner Losh <imp@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, Devin Teske <dteske@freebsd.org> Subject: Re: svn commit: r293227 - head/etc Message-ID: <5360EA7A-399F-4679-B58F-62D0112EA481@shxd.cx> In-Reply-To: <20160106125617.E968@besplex.bde.org> References: <201601052120.u05LKlQw074919@repo.freebsd.org> <1452038404.1320.46.camel@freebsd.org> <20160106125617.E968@besplex.bde.org>
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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 cond=
itions involving -i and adding -f abates them all.
--=20
Devin
> On Jan 5, 2016, at 6:48 PM, Bruce Evans <brde@optusnet.com.au> wrote:
>=20
> On Tue, 5 Jan 2016, Ian Lepore wrote:
>=20
>>> 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.
>=20
> "proper -f" is hard to parse. I think you mean:
>=20
> 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.
>=20
> 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.
>=20
>>> Modified: head/etc/rc
>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D
>>> --- 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} =3D "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} =3D "yes" ] || mount -ur /
>>> kill -INT 1
>>> fi
>>=20
>> 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.
>=20
> 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.
>=20
> So the only effect of this -f is to turn off -i, which can only be set
> if the FUD was justified.
>=20
> The correct fix seems to be 'unalias -a'.
>=20
> Bruce
>=20
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