Messages in this thread | | | From | Jann Horn <> | Date | Thu, 30 Apr 2020 05:00:03 +0200 | Subject | Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1 |
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On Thu, Apr 30, 2020 at 4:20 AM Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Wed, Apr 29, 2020 at 6:08 PM Bernd Edlinger > <bernd.edlinger@hotmail.de> wrote: > > > > I added the BIG FAT WARNNIG comments as a mitigation for that. > > Did you like those comments? > > No. > > What's the point olf saying "THIS CODE IS GARBAGE" and then expecting > that to make it ok? > > No,m that doesn't make it ok. It just means that it should have been > done differently. > > > Yes, exactly, the point is the caller is expected to call wait in that > > scenario, otherwise the -EAGAIN just repeats forever, that is an API > > change, yes, but something unavoidable, and the patch tries hard to > > limit it to cases where the live-lock or pseudo-dead-lock is unavoidable > > anyway. > > I'm getting really fed up with your insistence on that KNOWN BROKEN > garbage test-case. > > It's shit. The test-case is wrong. I've told you before. > > Your patch as-is breaks other cases that are *not* wrong in the kernel > currently, and that don't have test-cases because they JustWork(tm). > > The livelock isn't interesting. The test-case that shows it is pure > garbage, and is written wrong. > > IF that test-case hadn't been buggy in the first place, it would have > had ignored its child (or had a handler for SIGCHLD), and not > livelocked.
But if we go with Bernd's approach together with your restart suggestion, then simply doing PTRACE_ATTACH on two threads A and B would be enough to livelock, right?
tracer: PTRACE_ATTACHes to A B: enters de_thread() tracer: attempts to PTRACE_ATTACH to B
Now the tracer will loop on PTRACE_ATTACH, right?
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