Messages in this thread | | | Subject | Re: [PATCH v3 0/3] Actually fix freelist pointer vs redzoning | From | Vlastimil Babka <> | Date | Thu, 15 Oct 2020 11:44:15 +0200 |
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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.
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