Hi, On Thu, Sep 25, 2025 at 08:40:56PM +0000, Edgecombe, Rick P wrote: > On Sun, 2025-09-21 at 14:21 +0100, Mark Brown wrote: > > During the discussion of the clone3() support for shadow stacks concerns > > were raised from the glibc side that since it is not possible to reuse > > the allocated shadow stack[1]. This means that the benefit of being able > > ... > > > Security-wise, it seems reasonable that if you are leaving a shadow stack, > that > you could leave a token behind. But for the userspace scheme to back up the > SSP > by doing a longjmp() or similar I have some doubts. IIRC there were some cross > stack edge cases that we never figured out how to handle. > > As far as re-using allocated shadow stacks, there is always the option to > enable > WRSS (or similar) to write the shadow stack as well as longjmp at will. > > I think we should see a fuller solution from the glibc side before adding new > kernel features like this. (apologies if I missed it).
What do you mean by "a fuller solution from the glibc side"? A solution for re-using shadow stacks? Right now Glibc cannot do anything about shadow stacks for new threads because clone3 interface doesn't allow it. Thanks, Yury
