On Mon, May 8, 2017 at 8:26 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Mon, May 8, 2017 at 8:22 AM, Daniel Micay <danielmicay@xxxxxxxxx> wrote: >> On Mon, 2017-05-08 at 09:52 +0200, Ingo Molnar wrote: >>> >>> ... it's just not usable in that form for a regular maintenance flow. >>> >>> So what would be more useful is to add a specific Sparse check that >>> only checks >>> KERNEL_DS, to add it as a regular (.config driven) build option and >>> make sure the >>> kernel build has zero warnings. >>> >>> From that point on we can declare that this kind of bug won't occur >>> anymore, if >>> the Sparse implementation of the check is correct. >>> >>> But there's a (big) problem with that development model: Sparse is not >>> part of the >>> kernel tree and adding a feature to it while making the kernel depend >>> on that >>> brand new feature is a logistical nightmare. The overhead is quite >>> similar to >>> adding new features to a compiler - it happens at a glacial pace and >>> is only done >>> for major features really, at considerable expense. I don't think this >>> is an >>> adequate model for 'extended syntax checking' of the kernel, >>> especially when it >>> comes to correctness that has such obvious security impact. >>> >>> Thanks, >>> >>> Ingo >> >> There's the option of using GCC plugins now that the infrastructure was >> upstreamed from grsecurity. It can be used as part of the regular build >> process and as long as the analysis is pretty simple it shouldn't hurt >> compile time much. > > Well, and that the situation may arise due to memory corruption, not > from poorly-matched set_fs() calls, which static analysis won't help > solve. We need to catch this bad kernel state because it is a very bad > state to run in. Of course, I agree with Kees points on this and previous emails. A static analysis solution is hard to scale across functions and build time can suffer. I don't think the coverage will be good enough to consider this change and static analysis as similar. > > -Kees > > -- > Kees Cook > Pixel Security -- Thomas -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
