Messages in this thread |  | | | Date | Mon, 4 Sep 2006 15:00:27 -0700 (PDT) | | From | Linus Torvalds <> | | Subject | Re: Trouble with ptrace self-attach rule since kernel > 2.6.14 |
| |
On Mon, 4 Sep 2006, Andreas Hobein wrote: > > I've tested tracing child threads from the parent thread as well as tracing > siblings and parent threads from a child. All tests where successful when > reverting the above mentioned changes.
The problems tend to happen when the thread leader exits while one of the sub-threads is being traced, and the tracer thread ends up being re-parented to be the child of the traced thread (or something like that - I forget the exact details).
There was also some problem with the tracer doing an exit() without detaching, or something.
We may have fixed most of the problems since - Oleg has certainly been cleaning up some of this, and it's possible that the problems we had are ok now.
Even back when it was broken, _normal_ use never showed the problem (ie no well-behaved ptrace use would cause anything bad to happen). But the breakage was a local DoS attack, where you could either force an oops or a unkillable process, I forget which.
There was an exploit for at least one of the exploits, so maybe somebody could test that exploit together with the one-line revert.
That said, it sounds like both of the people who ever noticed this are reasonably happy with their work-arounds, so I'm hoping we can simply decide not to care, and just keep doing the simpler "you can't ptrace your own thread group" thing. That rule simply avoids a lot of special cases.
Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |