cvs commit: src/usr.bin/make job.c

[Max Okumoto]

Alexander Leidinger wrote:
> Max Okumoto <okumoto at ucsd.edu> wrote:> 
>> If I use mkdtemp(), there is a chance that someone with the
>> same UID could race to build the fifo. Do we care about
>> races with ourselves?  Or am I just being toooo paranoid? :-)

> Are you sure? mkdtemp() generates a "random" name like mkstemp() does, 
> so the race would have existed already before (but the probability is
> very low that two make instances generate the same name)...
> 
> Bye,
> Alexander.

Its not a race between two nice programs :-)  The function mkdtmp()
creates a uniq directory, but make would then need to create a fifo
in it. (This is two steps, and thus can allow a race)

Assume badmake has same uid, so it can create a file in the uniq
directory.  (Of course this means that the bad guy already has
your account.)

				Max

Normal pattern:
---------------------
make0: uses mkdtmp() to create dir /tmp/4321
make0: tries to create fifo /tmp/4321
make1: uses mkdtmp() to create dir /tmp/4321 but fails
make1: mkdtmp() next tries to create /tmp/4322 successs
make1: tries to create fifo /tmp/4322


Sort of DOS:
---------------------
make:	 uses mkdtmp() to create /tmp/1234/

badmake: watches for creation of /tmp/1234/ and
	 creates /tmp/1234/fifo.

make:	 tries to create /tmp/1234/fifo fails.