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Old 11-20-2007, 05:47 PM
"Dave Burns"
 
Default why does empty file /media/.hal-mtab-lock have suid bit set?

I stumbled upon the follwoing:

#rpm -qf /media/.hal-mtab-lock
file /media/.hal-mtab-lock is not owned by any package

#ls -la /media/.hal-mtab-lock
-rwS-----x 1 root root 0 Jun 25 12:44 /media/.hal-mtab-lock

# file /media/.hal-mtab-lock
/media/.hal-mtab-lock: setuid empty

I find this strange. By googling I get the impression it is a valid
hald file, but why the weird permissions?

Thanks,
Dave

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Old 11-20-2007, 10:46 PM
Les
 
Default why does empty file /media/.hal-mtab-lock have suid bit set?

HI, Dave,
This is a "lock" file, used to prevent multiple access to another file.
When the other file is opened by an application, that application
generates the lock file to signal that the file is in use. When the
application closes, the lock file is deleted and the next application in
the thread que for access can open and write to the file. It is to
prevent write errors on your disk.

Regards,
Les H
On Tue, 2007-11-20 at 08:47 -1000, Dave Burns wrote:
> I stumbled upon the follwoing:
>
> #rpm -qf /media/.hal-mtab-lock
> file /media/.hal-mtab-lock is not owned by any package
>
> #ls -la /media/.hal-mtab-lock
> -rwS-----x 1 root root 0 Jun 25 12:44 /media/.hal-mtab-lock
>
> # file /media/.hal-mtab-lock
> /media/.hal-mtab-lock: setuid empty
>
> I find this strange. By googling I get the impression it is a valid
> hald file, but why the weird permissions?
>
> Thanks,
> Dave
>

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Old 11-21-2007, 12:32 AM
"Dave Burns"
 
Default why does empty file /media/.hal-mtab-lock have suid bit set?

On Nov 20, 2007 1:46 PM, Les <hlhowell@pacbell.net> wrote:
> HI, Dave,
> This is a "lock" file, used to prevent multiple access to another file.
Thanks Les, but 'what is it?' was not the question. Why would a lock
file need to have world execute permissions, owner (root) read/write,
and SUID bit set? Harmless mistake? Sinister sneakiness? World
executable, owned by root, setuid, sounds pretty fishy. The only thing
that prevents me from panicking already is that the file is empty. But
I've heard of stranger things than this leaving a backdoor open.


I just shut down haldaemon, erased the lock file, and restarted
haldaemon, and now it is world-readable, root executable, and with the
t-bit set, which I don't remember what it means. Maybe haldaemon uses
the permissions as a sort of semaphore? Doesn't seem broken - yet.

#[root@linoleum archive]# ls -la /media/.hal-mtab-lock
---x---r-t 1 root root 0 Nov 20 15:27 /media/.hal-mtab-lock


Dave

> When the other file [snip]
> >
> > #ls -la /media/.hal-mtab-lock
> > -rwS-----x 1 root root 0 Jun 25 12:44 /media/.hal-mtab-lock
> >
> > # file /media/.hal-mtab-lock
> > /media/.hal-mtab-lock: setuid empty
> >
> > I find this strange. By googling I get the impression it is a valid
> > hald file, but why the weird permissions?

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