Messages in this thread | | | Date | Thu, 4 Oct 2012 13:28:25 -0700 | Subject | Re: [PATCH 1/4] module: add syscall to load module from fd | From | Kees Cook <> |
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On Wed, Oct 3, 2012 at 10:39 PM, Rusty Russell <rusty@rustcorp.com.au> wrote: > Kees Cook <keescook@chromium.org> writes: > >> On Thu, Sep 20, 2012 at 3:14 PM, Kees Cook <keescook@chromium.org> wrote: >>> As part of the effort to create a stronger boundary between root and >>> kernel, Chrome OS wants to be able to enforce that kernel modules are >>> being loaded only from our read-only crypto-hash verified (dm_verity) >>> root filesystem. Since the init_module syscall hands the kernel a module >>> as a memory blob, no reasoning about the origin of the blob can be made. >>> >>> Earlier proposals for appending signatures to kernel modules would not be >>> useful in Chrome OS, since it would involve adding an additional set of >>> keys to our kernel and builds for no good reason: we already trust the >>> contents of our root filesystem. We don't need to verify those kernel >>> modules a second time. Having to do signature checking on module loading >>> would slow us down and be redundant. All we need to know is where a >>> module is coming from so we can say yes/no to loading it. >>> >>> If a file descriptor is used as the source of a kernel module, many more >>> things can be reasoned about. In Chrome OS's case, we could enforce that >>> the module lives on the filesystem we expect it to live on. In the case >>> of IMA (or other LSMs), it would be possible, for example, to examine >>> extended attributes that may contain signatures over the contents of >>> the module. >>> >>> This introduces a new syscall (on x86), similar to init_module, that has >>> only two arguments. The first argument is used as a file descriptor to >>> the module and the second argument is a pointer to the NULL terminated >>> string of module arguments. >> >> Hi Rusty, >> >> Is this likely to land in the 3.7 change window? I'd really like to >> get the syscall number assigned so I can start sending patches to >> glibc, kmod, etc. My tree is here, FWIW: > > No, unfortunately it's a little late and there were issues with ARM > signoffs and syscall numbers... > >> http://git.kernel.org/?p=linux/kernel/git/kees/linux.git;a=shortlog;h=refs/heads/module-fd-syscall > > Messy merge due to the module signing stuff going in :(
Sure was! :) I've done the merge now (and sent the v5 patches). I think it looks pretty clean now.
> Please rebase on top of my kernel.org modules-next branch, and I'll pull > into my modules-wip branch for 3.8.
As Mimi mentioned, it would be really nice if this could land in 3.7. Can I maybe convince you? It's technically a small change, just with a lot of reordering of the calling code, but I think it's a relatively small change. The diff output is horrible due to extracting do_init_module, but the code changed is pretty minimal.
-Kees
-- Kees Cook Chrome OS Security
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