Messages in this thread | | | From | Matthew Garrett <> | Date | Mon, 24 Jun 2019 14:30:46 -0700 | Subject | Re: [PATCH V34 23/29] bpf: Restrict bpf when kernel lockdown is in confidentiality mode |
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On Mon, Jun 24, 2019 at 2:22 PM Daniel Borkmann <daniel@iogearbox.net> wrote: > Agree, for example, bpf_probe_write_user() can never write into > kernel memory (only user one). Just thinking out loud, wouldn't it > be cleaner and more generic to perform this check at the actual function > which performs the kernel memory without faulting? All three of these > are in mm/maccess.c, and the very few occasions that override the > probe_kernel_read symbol are calling eventually into __probe_kernel_read(), > so this would catch all of them wrt lockdown restrictions. Otherwise > you'd need to keep tracking every bit of new code being merged that > calls into one of these, no? That way you only need to do it once like > below and are guaranteed that the check catches these in future as well.
Not all paths into probe_kernel_read/write are from entry points that need to be locked down (eg, as far as I can tell ftrace can't leak anything interesting here).
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