On 11/22/21 11:06 AM, Brijesh Singh wrote: >> 3. Kernel accesses guest private memory via a kernel mapping. This one >> is tricky. These probably *do* result in a panic() today, but >> ideally shouldn't. > KVM has defined some helper functions to maps and unmap the guest pages. > Those helper functions do the GPA to PFN lookup before calling the > kmap(). Those helpers are enhanced such that it check the RMP table > before the kmap() and acquire a lock to prevent a page state change > until the kunmap() is called. So, in the current implementation, we > should *not* see a panic() unless there is a KVM driver bug that didn't > use the helper functions or a bug in the helper function itself. I don't think this is really KVM specific. Think of a remote process doing ptrace(PTRACE_POKEUSER) or pretty much any generic get_user_pages() instance. As long as the memory is mapped into the page tables, you're exposed to users that walk the page tables. How do we, for example, prevent ptrace() from inducing a panic()?
