Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode

On Mon, May 8, 2017 at 4:02 PM, Ingo Molnar [off-list ref] wrote:

* Kees Cook [off-list ref] wrote:

quoted

quoted

And yes, I realize that there were other such bugs and that such bugs might
occur in the future - but why not push the overhead of the security check to
the kernel build phase? I.e. I'm wondering how well we could do static
analysis during kernel build - would a limited mode of Sparse be good enough
for that? Or we could add a new static checker to tools/, built from first
principles and used primarily for extended syntactical checking.

Static analysis is just not going to cover all cases. We've had vulnerabilities
where interrupt handlers left KERNEL_DS set, for example. [...]

Got any commit ID of that bug - was it because a function executed by the
interrupt handler leaked KERNEL_DS?

I think Kees might be talking about
https://bugs.chromium.org/p/project-zero/issues/detail?id=822, fixed in
commit e6978e4bf181fb3b5f8cb6f71b4fe30fbf1b655c. The issue was that
perf code that can run in pretty much any context called access_ok().