Messages in this thread | | | From | Kees Cook <> | Date | Tue, 6 Mar 2018 14:31:05 -0800 | Subject | Re: + mm-relax-ptrace-mode-in-process_vm_readv2.patch added to -mm tree |
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On Tue, Mar 6, 2018 at 10:03 AM, Alexey Dobriyan <adobriyan@gmail.com> wrote: > On Tue, Mar 06, 2018 at 08:42:19PM +0300, Alexey Dobriyan wrote: >> On Mon, Mar 05, 2018 at 05:02:08PM -0800, Kees Cook wrote: >> > On Mon, Mar 5, 2018 at 4:07 PM, <akpm@linux-foundation.org> wrote: >> >> > > It is more natural to check for read-from-memory permissions in case of >> > > process_vm_readv() as PTRACE_MODE_ATTACH is equivalent to write >> > > permissions. >> > >> > NAK, this weakens the existing permission model for reading >> >> What if existing permission model is overezealous? >> >> /proc/*/auxv, /proc/*/environ, /proc*/cmdline, /proc/*/mem opened >> for reading and process_vm_readv(2) should do PTRACE_MODE_READ and >> everything else should do PTRACE_MODE_ATTACH. > > Or in other words: > > what if there should be 3 levels: > 1) permission to write to address space > 2) permission to read arbitrarily from adress space > 3) permission to read auxv, argv and envp > > Current code conflates (1) and (2).
There is also:
4) permission to read address layout (e.g. access to /proc/$pid/maps)
1 and 2 require ATTACH 3 and 4 require READ
ATTACH is a higher bar, and I think it is appropriate here, still, for 2, since being able to examine secrets in memory should be considered a security boundary.
Is there something you're trying from userspace that is being blocked?
-Kees
-- Kees Cook Pixel Security
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