issue with unsetting 'arch' flag

[Garrett Cooper]

On Wed, Oct 6, 2010 at 10:35 AM, Alexander Best <arundel at freebsd.org> wrote:
> On Wed Oct  6 10, Garrett Cooper wrote:
>> On Tue, Oct 5, 2010 at 4:50 PM, Alexander Best <arundel at freebsd.org> wrote:
>> > hi there,
>> >
>> > i think the following example shows the problem better than a long explanation:
>> >
>> > `touch ftest && chflags arch ftest && chflags -vv 0 ftest`.
>> >  ^^non-root     ^^root                ^^non-root
>> >
>> > chflags claims to have cleared the 'arch' flag (which should be impossible as
>> > non-root user), but indeed has done nothing.
>> >
>> > i've tried the same with 'sappnd' and that works as can be expected.
>> >
>> > The issue was confirmed to exist in HEAD (me), stable/8 (pgollucc1, jpaetzel)
>> > and stable/7 (nox).
>> > On stable/6 it does NOT exist (jpaetzel). chflags properly fails with EPERM.
>>
>>     Fails for me when I call the syscall directly, as I would expect,
>> and passes when I'm superuser:
>>
>> $ ./test_chflags
>> (uid, euid) = (1000, 1000)
>> test_chflags: chflags: Operation not permitted
>> test_chflags: lchflags: Operation not permitted
>> $ sudo ./test_chflags
>> (uid, euid) = (0, 0)
>>
>>     According to my basic inspection in strtofflags
>> (.../lib/libc/gen/strtofflags.c), it works as well.
>>     And last but not least, executing the commands directly on the CLI work:
>>
>> $ tmpfile=`mktemp /tmp/chflags.XXXXXX`
>> $ chflags arch $tmpfile
>> chflags: /tmp/chflags.nQm1IL: Operation not permitted
>> $ rm $tmpfile
>> $ tmpfile=`mktemp /tmp/chflags.XXXXXX`
>> $ sudo chflags arch $tmpfile
>> $ sudo chflags noarch $tmpfile
>> $ rm $tmpfile
>
> thanks for your test app and helping out with this problem. i'm not sure
> however you understood the problem. probably i didn't explain it right:
>
> $ sudo rm -d /tmp/chflags.XXXXXX
> $ tmpfile=`mktemp /tmp/chflags.XXXXXX`
> $ sudo chflags arch $tmpfile
> $ chflags noarch $tmpfile
>
> is what's causing the problem. the last chflags call should fail, but it
> doesn't.

Sorry... my CLI based example was stupid. I meant:

$ tmpfile=`mktemp /tmp/chflags.XXXXXX`
$ chflags arch $tmpfile
chflags: /tmp/chflags.V2NpXR: Operation not permitted
$ chflags noarch $tmpfile
$ rm $tmpfile

Currently chflags(2) states:

     The SF_IMMUTABLE, SF_APPEND, SF_NOUNLINK, and SF_ARCHIVED flags may only
     be set or unset by the super-user.  Attempts to set these flags by non-
     super-users are rejected, >>> attempts by non-superusers to clear
flags that
     are already unset are silently ignored. <<<  These flags may be set at any
     time, but normally may only be unset when the system is in single-user
     mode.  (See init(8) for details.)

So this behavior is already well documented :). The EPERM section
should really note SF_ARCHIVED though (whoever added the flag forgot
to add that particular item to the ERRORS section).

>>     Your results may (but shouldn't) vary [unless your environment is
>> setup differently]...
>>     Please note that I'm using UFS2 with SUJ... not all filesystems
>> support this (ext2/3/4? msdosfs? ZFS?), so I would be careful about
>> which filesystem you pick and whether or not there's a bug where it's
>> not properly identifying that the operation you're attempting to
>> perform is valid.
>> Thanks,
>> -Garrett
>>
>> $ uname -a
>> FreeBSD bayonetta.local 9.0-CURRENT FreeBSD 9.0-CURRENT #9 r211309M:
>> Thu Aug 19 22:50:36 PDT 2010
>> root at bayonetta.local:/usr/obj/usr/src/sys/BAYONETTA  amd64

Thanks,
-Garrett