Messages in this thread |  | | Date | Thu, 2 Jul 2020 21:59:02 +0100 | From | Al Viro <> | Subject | Re: objtool clac/stac handling change.. |
| |
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 ;-/
|  |