Re: [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads

[Al Viro]

On Tue, Jun 15, 2021 at 02:36:38PM -0500, Eric W. Biederman wrote:
> 
> While thinking about the information leaks fixed in 77f6ab8b7768
> ("don't dump the threads that had been already exiting when zapped.")
> I realized the problem is much more general than just coredumps and
> exit_mm.  We have io_uring threads, PTRACE_EVENT_EXEC and
> PTRACE_EVENT_EXIT where ptrace is allowed to access userspace
> registers, but on some architectures has not saved them.

Wait a sec.  To have anything happen on PTRACE_EVENT_EXEC, you need the
fucker traced.  *IF* you want to go that way, at least make it conditional
upon the same thing.