On Fri, 15 Feb 2019 09:08:38 -0800 Linus Torvalds <[email protected]> wrote:
> On Fri, Feb 15, 2019 at 6:21 AM Steven Rostedt <[email protected]> wrote: > > > > - Have kprobes not use copy_from_user to access kernel addresses > > as this is now considered a security issue. > > No, you people are confused. > > The problem isn't that it's using a user access function on kernel memory. > > The problem is that it's using a user access function on a complete > garbage pointer that happens to not even be a valid pointer at all. > > You get a GP fault because the code tries to access an address at > 0x2e646c2f6374652f. > > That's not a valid pointer on x86-64. Nothing to do with user or > kernel, everything to do with "it's garbage". > > Switching over to probe_mem_read() just means that even non-canonical > address faults are ignored. But it has absolutely nothing to do with > "kernel addresses" or any security issues. > > So the patch looks like it might be ok, but the explanations for it > are garbage and only confuse the issue. > > Please fix the explanations, I don't want to have actively wrong > commit messages for when people start looking at things like this. > OK, I'll update the change log. Yeah, the bug is that we are reading possibly bad kernel memory, which is what kprobes do. Will update. -- Steve
