On Tue, Jan 3, 2017 at 2:07 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tuesday, January 3, 2017 10:29:33 AM CET Andy Lutomirski wrote: >> >> Hmm. What if we approached this a bit differently? We could add a >> single new personality bit ADDR_LIMIT_EXPLICIT. Setting this bit >> cause PER_LINUX32_3GB etc to be automatically cleared. > > Both the ADDR_LIMIT_32BIT and ADDR_LIMIT_3GB flags I guess? Yes. > >> When >> ADDR_LIMIT_EXPLICIT is in effect, prctl can set a 64-bit numeric >> limit. If ADDR_LIMIT_EXPLICIT is cleared, the prctl value stops being >> settable and reading it via prctl returns whatever is implied by the >> other personality bits. > > I don't see anything wrong with it, but I'm a bit confused now > what this would be good for, compared to using just prctl. > > Is this about setuid clearing the personality but not the prctl, > or something else? It's to avid ambiguity as to what happens if you set ADDR_LIMIT_32BIT and use the prctl. ISTM it would be nice for the semantics to be fully defined in all cases. --Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>