----- On Jun 28, 2018, at 7:29 PM, Andy Lutomirski [email protected] wrote: > On Thu, Jun 28, 2018 at 2:22 PM, Linus Torvalds > <[email protected]> wrote: >> On Thu, Jun 28, 2018 at 1:23 PM Andy Lutomirski <[email protected]> wrote: >>> >>> This is okay with me for a fix outside the merge window. Can you do a >>> followup for the next merge window that fixes it better, though? In >>> particular, TASK_SIZE is generally garbage. I think a better fix >>> would be something like adding a new arch-overridable helper like: >>> >>> static inline unsigned long current_max_user_addr(void) { return TASK_SIZE; >>> } >> >> We already have that. It's called "user_addr_max()". > > Nah, that one is more or less equivalent to TASK_SIZE_MAX, except that > it's different if set_fs() is used.
So which one would be right in this case ? AFAIU we want to ensure we don't populate regs->ip with a bogus address that would make SYSRET or other return to userspace instructions explode. Is that guaranteed by TASK_SIZE or TASK_SIZE_MAX (aliased by user_addr_max()) ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
