On Sun, 2018-09-02 at 18:38 -0700, Linus Torvalds wrote: > On Sun, Sep 2, 2018 at 6:32 PM Benjamin Herrenschmidt > <b...@kernel.crashing.org> wrote: > > > > Also, if we cross page boundaries with those guys then we have a bigger > > problem no ? we could fall off a vmalloc page into the nether or into > > an ioremap mapping no ? > > It's not used for vmalloc stuff. It's just regular kmalloc(). > > So it can cross pages, and it can fall off the end of memory, but it > can't do random stuff.
Ok, it might be worth adding a DEBUG_VM based (or similar) warning in case somebody ever thinks of passing a vmalloc pointer to it... As for falling out of the end of memory, yes it could be a real problem though I don't see why IO is any different than just hitting a non- mapped area in that regard. So we should probably keep an unused (readonly if possible) zero page at the end. Cheers, Ben.
