On Tue, Nov 16, 2021 at 11:00:23AM -0800, Casey Schaufler wrote: > On 11/16/2021 10:41 AM, Kees Cook wrote: > > On Tue, Nov 16, 2021 at 12:12:16PM +0300, Alexander Popov wrote: > > > What if the Linux kernel had a LSM module responsible for error handling policy? > > > That would require adding LSM hooks to BUG*(), WARN*(), KERN_EMERG, etc. > > > In such LSM policy we can decide immediately how to react on the kernel error. > > > We can even decide depending on the subsystem and things like that. > > That would solve the "atomicity" issue the WARN tracepoint solution has, > > and it would allow for very flexible userspace policy. > > > > I actually wonder if the existing panic_on_* sites should serve as a > > guide for where to put the hooks. The current sysctls could be replaced > > by the hooks and a simple LSM. > > Do you really want to make error handling a "security" issue? > If you add security_bug(), security_warn_on() and the like > you're begging that they be included in SELinux (AppArmor) policy. > BPF, too, come to think of it. Is that what you want? Yeah, that is what I was thinking. This would give the LSM a view into kernel state, which seems a reasonable thing to do. If system integrity is compromised, an LSM may want to stop trusting things. A dedicated error-handling LSM could be added for those hooks that implemented the existing default panic_on_* sysctls, and could expand on that logic for other actions. -- Kees Cook
