linux-kernel - Re: INFO: task hung in wdm

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Message-ID: <CACT4Y+Yv-T-MfW=mgzuD99tsfkmE5Tk6bBhio9KNtPTmXM4cEw@mail.gmail.com>
Date:   Tue, 11 Feb 2020 15:01:37 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Oliver Neukum <oneukum@...e.de>,
        syzbot <syzbot+854768b99f19e89d7f81@...kaller.appspotmail.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Jia-Ju Bai <baijiaju1990@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Colin King <colin.king@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        yuehaibing@...wei.com, Bjørn Mork <bjorn@...k.no>
Subject: Re: INFO: task hung in wdm_flush

On Mon, Feb 10, 2020 at 4:22 PM Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> On 2020/02/11 0:06, Dmitry Vyukov wrote:
> >> On Mon, Feb 10, 2020 at 4:03 PM Tetsuo Handa
> >> <penguin-kernel@...ove.sakura.ne.jp> wrote:
> >>>
> >>> On 2020/02/10 21:46, Tetsuo Handa wrote:
> >>>> On 2020/02/10 19:09, Dmitry Vyukov wrote:
> >>>>> You may also try on the exact commit the bug was reported, because
> >>>>> usb-fuzzer is tracking branch, things may change there.
> >>>>
> >>>> OK. I explicitly tried
> >>>>
> >>>>   #syz test: https://github.com/google/kasan.git e5cd56e94edde38ca4dafae5a450c5a16b8a5f23
> >>>>
> >>>> but syzbot still cannot reproduce this bug using the reproducer...
> >>>
> >>> It seems that there is non-trivial difference between kernel config in dashboard
> >>> and kernel config in "syz test:" mails. Maybe that's the cause...
> >
> >
> > syzkaller runs oldconfig when building any kernels:
> > https://github.com/google/syzkaller/blob/master/pkg/build/linux.go#L56
> > Is that difference what oldconfig produces?
> >
>
> Here is the diff (with "#" lines excluded) between dashboard and "syz test:" mails.
> I feel this difference is bigger than what simple oldconfig would cause.
>
> $ curl 'https://syzkaller.appspot.com/text?tag=KernelConfig&x=8cff427cc8996115' | sort > dashboard

I think you took a wrong config as a base.
This 8cff427cc8996115 was only used for crashes without reproducers as
far as I see, so it can't be used for patch testing.
I would expect the one used for last patch testing is this one:
https://syzkaller.appspot.com/text?tag=KernelConfig&x=8847e5384a16f66a
associated with this crash:
ci2-upstream-usb2019/09/23 13:26https://github.com/google/kasan.git
usb-fuzzere0bd8d79d96e88f3

I checked at least CONFIG_DYNAMIC_DEBUG, and it matches what was used
for patch testing.
So everything seems right to me as far as I see.



> $ curl 'https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162' | sort > syz-test
> $ diff -u dashboard syz-test | grep -vF '#' | grep '^[+-]'
> --- dashboard   2020-02-11 00:19:14.793977153 +0900
> +++ syz-test    2020-02-11 00:19:15.659977108 +0900
> -CONFIG_BLK_DEV_LOOP_MIN_COUNT=16
> +CONFIG_BLK_DEV_LOOP_MIN_COUNT=8
> -CONFIG_BUG_ON_DATA_CORRUPTION=y
> -CONFIG_DEBUG_CREDENTIALS=y
> -CONFIG_DEBUG_PER_CPU_MAPS=y
> -CONFIG_DEBUG_PLIST=y
> -CONFIG_DEBUG_SG=y
> -CONFIG_DEBUG_VIRTUAL=y
> +CONFIG_DEVMEM=y
> +CONFIG_DEVPORT=y
> +CONFIG_DMA_OF=y
> -CONFIG_DYNAMIC_DEBUG=y
> -CONFIG_DYNAMIC_MEMORY_LAYOUT=y
> +CONFIG_HID_REDRAGON=y
> +CONFIG_IRQCHIP=y
> -CONFIG_LSM="lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
> +CONFIG_LSM="yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
> -CONFIG_MAC80211_HWSIM=y
> +CONFIG_MAGIC_SYSRQ=y
> +CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE=0x1
> +CONFIG_MAGIC_SYSRQ_SERIAL=y
> +CONFIG_NET_TC_SKB_EXT=y
> +CONFIG_OF=y
> +CONFIG_OF_ADDRESS=y
> +CONFIG_OF_GPIO=y
> +CONFIG_OF_IOMMU=y
> +CONFIG_OF_IRQ=y
> +CONFIG_OF_KOBJ=y
> +CONFIG_OF_MDIO=y
> +CONFIG_OF_NET=y
> -CONFIG_PGTABLE_LEVELS=5
> +CONFIG_PGTABLE_LEVELS=4
> +CONFIG_PWRSEQ_EMMC=y
> +CONFIG_PWRSEQ_SIMPLE=y
> +CONFIG_RTLWIFI_DEBUG=y
> -CONFIG_SECURITYFS=y
> +CONFIG_STRICT_DEVMEM=y
> +CONFIG_THERMAL_OF=y
> +CONFIG_USB_CHIPIDEA_OF=y
> +CONFIG_USB_DWC3_OF_SIMPLE=y
> -CONFIG_USB_RAW_GADGET=y
> +CONFIG_USB_SNP_UDC_PLAT=y
> -CONFIG_VIRTIO_BLK_SCSI=y
> -CONFIG_VIRT_WIFI=y
> -CONFIG_X86_5LEVEL=y