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Subject: Re: INFO: task hung in wdm_flush
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Oliver Neukum <oneukum@suse.de>,
        syzbot <syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Jia-Ju Bai <baijiaju1990@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Colin King <colin.king@canonical.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        yuehaibing@huawei.com, =?UTF-8?Q?Bj=c3=b8rn_Mork?= <bjorn@mork.no>
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From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <bbf26ea3-c11c-1cd2-0072-b78634ae9579@i-love.sakura.ne.jp>
Date:   Tue, 11 Feb 2020 00:21:56 +0900
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On 2020/02/11 0:06, Dmitry Vyukov wrote:
>> On Mon, Feb 10, 2020 at 4:03 PM Tetsuo Handa
>> <penguin-kernel@i-love.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
$ 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