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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 22 Mar 2021 08:53:47 +0100
Message-ID: <CACT4Y+bvakfNhVs29QvbY6Z8Pw0zmAUKGWM-DD5DcPZW5ny90A@mail.gmail.com>
Subject: Re: [RFC PATCH 2/2] integrity: double check iint_cache was initialized
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Mimi Zohar <zohar@linux.ibm.com>, linux-integrity@vger.kernel.org,
        James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Eric Biggers <ebiggers@kernel.org>
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On Mon, Mar 22, 2021 at 8:11 AM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> On 2021/03/20 5:03, Mimi Zohar wrote:
> > The integrity's "iint_cache" is initialized at security_init().  Only
> > after an IMA policy is loaded, which is initialized at late_initcall,
> > is a file's integrity status stored in the "iint_cache".
> >
> > All integrity_inode_get() callers first verify that the IMA policy has
> > been loaded, before calling it.  Yet for some reason, it is still being
> > called, causing a NULL pointer dereference.
> >
> > As reported by Dmitry Vyukov:
> > in qemu:
> > qemu-system-x86_64       -enable-kvm     -machine q35,nvdimm -cpu
> > max,migratable=off -smp 4       -m 4G,slots=4,maxmem=16G        -hda
> > wheezy.img      -kernel arch/x86/boot/bzImage   -nographic -vga std
> >  -soundhw all     -usb -usbdevice tablet  -bt hci -bt device:keyboard
> >    -net user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net
> > nic,model=virtio-net-pci   -object
> > memory-backend-file,id=pmem1,share=off,mem-path=/dev/zero,size=64M
> >   -device nvdimm,id=nvdimm1,memdev=pmem1  -append "console=ttyS0
> > root=/dev/sda earlyprintk=serial rodata=n oops=panic panic_on_warn=1
> > panic=86400 lsm=smack numa=fake=2 nopcid dummy_hcd.num=8"   -pidfile
> > vm_pid -m 2G -cpu host
> >
>
> I tried similar command line (without "-enable-kvm" and without "-cpu host"
> as I'm running from VMware, without "-soundhw all", without "-machine q35,nvdimm"
> and "-device nvdimm,id=nvdimm1,memdev=pmem1" etc.) on 5.12-rc4. While I was finally
> able to hit similar crash when I used "-smp 1" instead of "-smp 4", I suspect
> this is not a integrity module's problem but a memory initialization/corruption
> problem, for I got various different crashes (INT3) at memory allocation when
> I was trimming command line options trying to reproduce the same crash.
>
> Dmitry, do you get different crashes by changing command line arguments?

No, I have not seen any other crashes, one the reported one.