linux-kernel - Re: [PATCH] module: Add CONFIG_MODULE_LOAD_IN

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Message-ID: <ZSYGmQhlGKmYXENG@bombadil.infradead.org>
Date:   Tue, 10 Oct 2023 19:21:13 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     "Joey Jiao (QUIC)" <quic_jiangenj@...cinc.com>
Cc:     "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] module: Add CONFIG_MODULE_LOAD_IN_SEQUENCE option

Please find a good email client to reply to patches.

On Wed, Oct 11, 2023 at 01:57:58AM +0000, Joey Jiao (QUIC) wrote:
> Hi Luis,
> 
> > How is ignoring an error ensuring ordering?
> The change is just to disable the schedule_work.

That's different and can be made clearer. Try:

if (!IS_ENABLED(CONFIG_FOO))
	schedule_stuff

> > Why are you making this only now be called with this new kconfig option?
> This sequence loading is especially helpful for syzkaller coverage decoding.
> When kaslr is disabled, address inside core kernel is fixed, so syzkaller can always get right function/line number from addr2line.
> But module address keeps change across rebooting, in first booting, it might be loaded at X1, and at X2 after reboot, and at X3 after another reboot.
> In this way, syzkaller just can't decode correctly for module address. And syzkaller currently uses PC and branch info for coverage guided things.
> 
> There was a discussion previously here https://groups.google.com/g/syzkaller/c/1Pnm_BjrZO8/m/WOyAKx8ZAgAJ for modprobe.

You are missing my point, you are disabling in effect a piece of code
where it was not before.

  Luis