Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK_SIZE

On Thu, Jun 28, 2018 at 1:23 PM Andy Lutomirski [off-list ref] 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()".

It's the limit we use for user accesses.

That said, I don't see why we should even check the IP. It's not like
that's done by signal handling either.

                     Linus