Re: World writable pid and lock files.

[Mike Mestnik <cheako@mikemestnik.net>]

Henrique de Moraes Holschuh wrote:
> You know, it would help if you actually read what you replied to.
>
>   
start-stop-daemon(8) says
/proc/pid/exe is used.  On my system that is a symbolic link.  What I 
wold do if I was to write start-stop-daemon is read the link and match 
that value with the name passed to --exec.  This would have nothing to do
with inode numbers.  However start-stop-daemon might look at the inode 
number of the dereferenced link and match that to the inode number of 
the name passed to --exec.  This should also match, though there is a 
race condition here.  I'm a bit confused as /proc/pid/exe should be 
usable for debuggers like gdb.

cheako@www:~$ cp /bin/bash .
cheako@www:~$ ./bash
cheako@www:~$ ls -arlt /proc/$$/exe
lrwxrwxrwx 1 cheako cheako 0 May 15 12:42 /proc/30288/exe -> 
/home/cheako/bash
cheako@www:~$ rm bash
cheako@www:~$ ls -arlt /proc/$$/exe
lrwxrwxrwx 1 cheako cheako 0 May 15 12:42 /proc/30288/exe -> 
/home/cheako/bash (deleted)

So /proc/$$/exe has some implementation issues.