careful with that umount options, Eugene

careful with that umount options, Eugene

[Harald Dunkel]

Hi folks

by accident I pasted

	umount ls -al /mnt/

into bash. My bad. AFAICT /proc was umounted immediately, the
rest died slowly. Don't try this at home.

Point is, according to the man page this command line should
have triggered an error message. "umount ls -al" doesn't make
sense.

Do you think the command line parser could be fixed?

util-linux is version 2.29.2-1+deb9u1, as included in Debian.
Of course I checked the diff for umount.c between 2.29 and
3.34-rc2. Apparently the getopt code has been improved, but I
did not notice a fix for this particular problem.


Thanx in advance. Keep on your good work
Harri

Re: careful with that umount options, Eugene

[Václav Doležal]

Hi,
-a (--all) and -l (--lazy) are valid options and GNU getopt
reorders arguments (options first) so umount has seen

    umount --all --lazy ls /mnt/

and because --all mode doesn't take any arguments, it ignored
'ls /mnt/'. Modifying this to error on extra args should be
trivial.

As for the command unmounting /proc when it should be ignored,
it is caused by umounting root dir with --lazy (MNT_DETACH)
option. See umount2(2).

Regards,
Václav Doležal

On 2019-06-04 at 13:51 Harald Dunkel wrote:
> Hi folks
> 
> by accident I pasted
> 
>     umount ls -al /mnt/
> 
> into bash. My bad. AFAICT /proc was umounted immediately, the
> rest died slowly. Don't try this at home.
> 
> Point is, according to the man page this command line should
> have triggered an error message. "umount ls -al" doesn't make
> sense.
> 
> Do you think the command line parser could be fixed?
> 
> util-linux is version 2.29.2-1+deb9u1, as included in Debian.
> Of course I checked the diff for umount.c between 2.29 and
> 3.34-rc2. Apparently the getopt code has been improved, but I
> did not notice a fix for this particular problem.
> 
> 
> Thanx in advance. Keep on your good work
> Harri

Re: careful with that umount options, Eugene

[Karel Zak]

On Tue, Jun 04, 2019 at 01:51:58PM +0200, Harald Dunkel wrote:
> Hi folks
> 
> by accident I pasted
> 
> 	umount ls -al /mnt/
> 
> into bash. My bad. AFAICT /proc was umounted immediately, the
> rest died slowly. Don't try this at home.

Fixed ... new version:

 # umount ls -al /mnt/
 umount: unexpected arguments
 Try 'umount --help' for more information.

Thanks for your report.

   Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: careful with that umount options, Eugene

[Theodore Ts'o]

On Thu, Jun 06, 2019 at 02:59:47PM +0200, Karel Zak wrote:
> On Tue, Jun 04, 2019 at 01:51:58PM +0200, Harald Dunkel wrote:
> > Hi folks
> > 
> > by accident I pasted
> > 
> > 	umount ls -al /mnt/
> > 
> > into bash. My bad. AFAICT /proc was umounted immediately, the
> > rest died slowly. Don't try this at home.
> 
> Fixed ... new version:
> 
>  # umount ls -al /mnt/
>  umount: unexpected arguments
>  Try 'umount --help' for more information.

Hmm...  Should we also prevent a lazy unmount of the root file system?

	       	       	       	 - Ted

Re: careful with that umount options, Eugene

[Karel Zak]

On Thu, Jun 06, 2019 at 07:31:47PM -0400, Theodore Ts'o wrote:
> On Thu, Jun 06, 2019 at 02:59:47PM +0200, Karel Zak wrote:
> > On Tue, Jun 04, 2019 at 01:51:58PM +0200, Harald Dunkel wrote:
> > > Hi folks
> > > 
> > > by accident I pasted
> > > 
> > > 	umount ls -al /mnt/
> > > 
> > > into bash. My bad. AFAICT /proc was umounted immediately, the
> > > rest died slowly. Don't try this at home.
> > 
> > Fixed ... new version:
> > 
> >  # umount ls -al /mnt/
> >  umount: unexpected arguments
> >  Try 'umount --help' for more information.
> 
> Hmm...  Should we also prevent a lazy unmount of the root file system?

Not sure if we want to maintain extra rule/restriction in userspace.
Is there any reason why this feature is supported by kernel?

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: careful with that umount options, Eugene

[Theodore Ts'o]

On Fri, Jun 07, 2019 at 09:20:03AM +0200, Karel Zak wrote:
> > Hmm...  Should we also prevent a lazy unmount of the root file system?
> 
> Not sure if we want to maintain extra rule/restriction in userspace.
> Is there any reason why this feature is supported by kernel?

I certainly can't think of one.  I'll raise on linux-fsdevel; if
there's no good reason ever, I agree that it's probably better to
restrict in the kernel.

					- Ted