On Tue, Feb 26, 2019 at 06:18:25PM +0100, Andrey Konovalov wrote: > On Fri, Feb 22, 2019 at 11:55 PM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > > > On 2/22/19 4:53 AM, Andrey Konovalov wrote: > > > The following testing approaches has been taken to find potential issues > > > with user pointer untagging: > > > > > > 1. Static testing (with sparse [3] and separately with a custom static > > > analyzer based on Clang) to track casts of __user pointers to integer > > > types to find places where untagging needs to be done. > > > > First of all, it's really cool that you took this approach. Sounds like > > there was a lot of systematic work to fix up the sites in the existing > > codebase. > > > > But, isn't this a _bit_ fragile going forward? Folks can't just "make > > sparse" to find issues with missing untags. > > Yes, this static approach can only be used as a hint to find some > places where untagging is needed, but certainly not all. > > > This seems like something > > where we would ideally add an __tagged annotation (or something) to the > > source tree and then have sparse rules that can look for missed untags. > > This has been suggested before, search for __untagged here [1]. > However there are many places in the kernel where a __user pointer is > casted into unsigned long and passed further. I'm not sure if it's > possible apply a __tagged/__untagged kind of attribute to non-pointer > types, is it? > > [1] https://patchwork.kernel.org/patch/10581535/ It's something that should need to be added to sparse since it's different from what sparse already have (the existing __bitwise and concept of address-space doesn't seem to do the job here). -- Luc Van Oostenryck
