Re: [PATCH 1/3] kernel/sysctl: support setting sysctl parameters from kernel command line

On Fri, Apr 03, 2020 at 04:57:51PM -0700, Kees Cook wrote:

On Thu, Apr 02, 2020 at 08:59:32PM +0000, Luis Chamberlain wrote:

quoted

We modify the copied bootparams to allow new sysctls to map to old boot params?

This strdup is so that the
command line can have '\0's injected while it steps through the args
(and for doing the . and / replacement).

Please ignore the const feedback then.

quoted

This is the least cumbersome solution I could think of. Other things
would require things like using qemu, etc. That seems much more messsy.

Yes. Doing an internal extension isn't testing the actual code.

But it would.

quoted

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This is an external interface (boot params), so
I'd rather an external driver handle that testing. We don't have a
common method to do that with the kernel, though.

Right... which begs the question now -- how do we test this sort of
stuff? The above would at least get us coverage while we iron something
more generic out for boot params.

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That would test both cases with one kernel.

You could then also add a bogus new sysctl which also expands to a silly
raw boot param to test the wrapper you are providing. That would be the
only new test syctl you would need to add.

Sure, that seems reasonable. Supporting externally driven testing makes
sense for this.

But again, what exactly?

I don't think anything is needed for this series. It can be boot tested
manually.

Why test it manually when it could be tested automatically with a new kconfig?

  Luis