Comment 18 for bug 1673976

That glibc change has caused the assert to go away, but QEMU's spawn(CLONE_VFORK) still does not have the "always waits for child" semantics that glibc has assumed since glibc commit 4b4d4056bb154. The child and the parent will end up racing each other, and the child will never be able to write to the parent's address space. I think that the effect of that race will be that if the child fails (for instance if a bad filename is passed and exec() fails) the parent will never notice and will return a success code from the spawn function when it should not.

So there remains a QEMU bug here; though it is also the case that I can't see any way we can fix it.