Re: [RFC PATCH 04/13] powerpc/dexcr: Support userspace ROP protection
From: Benjamin Gray <hidden>
Date: 2023-03-07 05:38:17
Also in:
linux-hardening, lkml
On Tue, 2023-03-07 at 15:05 +1000, Nicholas Piggin wrote:
I think it is not quite per-process? I don't actually know how the user toolchain side is put together, but I'm thinking we can not give it a new salt on fork(), but we could on exec(). I think we could actually give each thread their own salt within a process too, right?
Yeah, the error case is we return further than we called in a given execution context. A forked child may return after the fork, meaning it needs the same key as the parent for the hashchk to work. Exec can get a new key because we can't return with any existing hashes. I haven't seen enough of kernel thread support to know if/how we can give threads their own key. I believe they go through the fork() call that copies the parent key currently.