On Tue, Dec 12, 2017 at 10:40:30AM +0000, Will Deacon wrote: > On Mon, Dec 11, 2017 at 11:23:09AM -0800, Kees Cook wrote: > > On Mon, Dec 11, 2017 at 6:07 AM, Will Deacon <will.deacon@xxxxxxx> wrote: > > > On Thu, Dec 07, 2017 at 10:50:38AM -0800, Kees Cook wrote: > > >> My question is mainly: why not just use copy_*() everywhere instead? > > >> Having these things so spread out makes it fragile, and there's very > > >> little performance benefit from using __copy_*() over copy_*(). > > > > > > I think that's more of a general question. Why not just remove the __ > > > versions from the kernel entirely if they're not worth the perf? > > > > That has been something Linus has strongly suggested in the past, so > > I've kind of been looking for easy places to drop the __copy_* > > versions. :) > > Tell you what then: I'll Ack the arm64 patch if it's part of a series > removing the thing entirely :p > > I guess we'd still want to the validation of the whole sigframe though, > so we don't end up pushing half a signal stack before running into an > access_ok failure? That's an interesting question. In many cases access_ok() might become redundant, but for syscalls that you don't want to have side-effects on user memory on failure it's still relevant. In the signal case we'd still an encompassing access_ok() to prevent stack guard overruns, because the signal frame can be large and isn't written or read contiguously or in a well-defined order. Cheers ---Dave
