On Thu, Jul 02, 2020 at 01:32:34PM -0700, Linus Torvalds wrote: > Ugh, the above is bad anyway. > > It doesn't use _ASM_EXTABLE_UA, so it won't warn about the noncanonical cases.
FWIW, the address is inside a sigframe we decided to build, so noncanonical addresses shouldn't occur in practice. > Yeah, it would need to be turned into a "jump out" instead of just "jump > over". > > Which it damn well should do anyway., > > That code should be taken behind a shed and shot. It does so many > things wrong that it's not even funny. It shouldn't do stac/clac on > its own. > > At least it could use the "user_insn()" helper, which does it inside > the asm itself, has the right might_fault() marking (but not the > address check), and which can be trivially changed to have the fixup > jump be to after the "ASM_CLAC". I'm not sure it's the right solution in this case. Look at the call chain and the stuff done nearby (that __clear_user(), for example)... I'm not saying that this code is not awful - it certainly is. But it's not that simple, unfortunately ;-/
