On 10/15/20 10:23 AM, Christopher Lameter wrote:
On Wed, 14 Oct 2020, Kees Cook wrote:
Note on patch 2: Christopher NAKed it, but I actually think this is a
reasonable thing to add -- the "too small" check is only made when built
with CONFIG_DEBUG_VM, so it *is* actually possible for someone to trip
over this directly, even if it would never make it into a released
kernel. I see no reason to just leave this foot-gun in place, though, so
we might as well just fix it too. (Which seems to be what Longman was
similarly supporting, IIUC.)
Well then remove the duplication of checks. The NAK was there because it
seems that you were not aware of the existing checks.
Anyway, if patch 2 stays NAKed, that's fine. It's entirely separable,
and the other 2 can land. :)
Just deal with the old checks too and it will be fine.
Yeah, the existing check is under CONFIG_DEBUG_VM, which means it's not active
on some configurations. Creating a cache is not exactly fast path operation, so
I would remove this guard.
As for the minimum size check, I would probably remove it (but watch out if
SLAB/SLOB can handle it). It's not effective to use slab cache for 4-byte
objects, but why make it an error.
