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Subject: Re: KASAN: use-after-free Write in irq_bypass_register_consumer
To:     Eric Biggers <ebiggers3@gmail.com>,
        "Lan, Tianyu" <tianyu.lan@intel.com>
Cc:     syzbot 
        <bot+7ad82526b98c64c90062275162dacfa48c20dbd3@syzkaller.appspotmail.com>,
        borntraeger@de.ibm.com, cornelia.huck@de.ibm.com, david@redhat.com,
        Dmitry Vyukov <dvyukov@google.com>,
        "H. Peter Anvin" <hpa@zytor.com>, jschoenh@amazon.de,
        kvm <kvm@vger.kernel.org>,
        "linux-kernel@vger kernel org" <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim Krcmar <rkrcmar@redhat.com>,
        syzkaller-bugs@googlegroups.com,
        Thomas Gleixner <tglx@linutronix.de>,
        the arch/x86 maintainers <x86@kernel.org>
References: <001a1143e716efd3a9055cc8696b@google.com>
 <001a1146f1146fe0b505605e42c1@google.com>
 <CAOLK0pxR1qJC3sT2QoHgj-ys7FgFqY8724Xo9CLjWxi439ZrTw@mail.gmail.com>
 <91a32ec1-64e7-8b6b-9464-6599dd6735ad@intel.com>
 <20180126232755.z3gtqrm2oz6sp2t6@gmail.com>
From:   Tianyu Lan <lantianyu1986@gmail.com>
Message-ID: <d630a4c9-04ba-9e41-1f7b-11c59b2cd8e4@gmail.com>
Date:   Mon, 29 Jan 2018 13:29:48 +0800
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On 1/27/2018 7:27 AM, Eric Biggers wrote:
> On Sat, Dec 16, 2017 at 04:37:02PM +0800, Lan, Tianyu wrote:
>> The root cause is that kvm_irqfd_assign() and kvm_irqfd_deassign() can't
>> be run in parallel. Some data structure(e.g, irqfd->consumer) will be
>> crashed because irqfd may be freed in deassign path before they are used
>> in assign path. The other data maybe used in deassign path before
>> initialization. Syzbot test hit such case. Add mutx between
>> kvm_irqfd_assign() and kvm_irqfd_deassign() can fix such issue. Will
>> send patch to fix it.
>>
>> On 12/16/2017 12:53 PM, Tianyu Lan wrote:
>>> I reproduced the issue. Will have a look.
>>>
>>> -- Best regards Tianyu Lan 2017-12-15 18:14 GMT+08:00 syzbot
>>> <bot+7ad82526b98c64c90062275162dacfa48c20dbd3@syzkaller.appspotmail.com>:
>>>> syzkaller has found reproducer for the following crash on
>>>> 82bcf1def3b5f1251177ad47c44f7e17af039b4b
>>>> git://git.cmpxchg.org/linux-mmots.git/master
>>>> compiler: gcc (GCC) 7.1.1 20170620
>>>> .config is attached
>>>> Raw console output is attached.
>>>> C reproducer is attached
>>>> syzkaller reproducer is attached. Seehttps://goo.gl/kgGztJ
>>>> for information about syzkaller reproducers
>>>>
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in __list_add include/linux/list.h:64 [inline]
>>>> BUG: KASAN: use-after-free in list_add include/linux/list.h:79 [inline]
>>>> BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4b4/0x500
>>>> virt/lib/irqbypass.c:217
>>>> Write of size 8 at addr ffff8801cdf51180 by task syzkaller436086/15031
>>>>
>>>> CPU: 1 PID: 15031 Comm: syzkaller436086 Not tainted 4.15.0-rc2-mm1+ #39
>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>>> Google 01/01/2011
>>>> Call Trace:
>>>>    __dump_stack lib/dump_stack.c:17 [inline]
>>>>    dump_stack+0x194/0x257 lib/dump_stack.c:53
>>>>    print_address_description+0x73/0x250 mm/kasan/report.c:252
>>>>    kasan_report_error mm/kasan/report.c:351 [inline]
>>>>    kasan_report+0x25b/0x340 mm/kasan/report.c:409
>>>>    __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
>>>>    __list_add include/linux/list.h:64 [inline]
>>>>    list_add include/linux/list.h:79 [inline]
>>>>    irq_bypass_register_consumer+0x4b4/0x500 virt/lib/irqbypass.c:217
>>>>    kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
>>>>    kvm_irqfd+0x137f/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
>>>>    kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2992
>>>>    vfs_ioctl fs/ioctl.c:46 [inline]
>>>>    do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>>>>    SYSC_ioctl fs/ioctl.c:701 [inline]
>>>>    SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>>>    entry_SYSCALL_64_fastpath+0x1f/0x96
>>>> RIP: 0033:0x44d379
>>>> RSP: 002b:00007fc5ff9a9d08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>>>> RAX: ffffffffffffffda RBX: 00007fc5ff9aa700 RCX: 000000000044d379
>>>> RDX: 0000000020080fe0 RSI: 000000004020ae76 RDI: 0000000000000005
>>>> RBP: 00000000007ff900 R08: 00007fc5ff9aa700 R09: 00007fc5ff9aa700
>>>> R10: 00007fc5ff9aa700 R11: 0000000000000246 R12: 0000000000000000
>>>> R13: 00000000007ff8ff R14: 00007fc5ff9aa9c0 R15: 0000000000000000
>>>>
>>>> Allocated by task 15031:
>>>>    save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>>>>    set_track mm/kasan/kasan.c:459 [inline]
>>>>    kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>>>>    kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3614
>>>>    kmalloc include/linux/slab.h:516 [inline]
>>>>    kzalloc include/linux/slab.h:705 [inline]
>>>>    kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
>>>>    kvm_irqfd+0x16c/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
>>>>    kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2992
>>>>    vfs_ioctl fs/ioctl.c:46 [inline]
>>>>    do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>>>>    SYSC_ioctl fs/ioctl.c:701 [inline]
>>>>    SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>>>    entry_SYSCALL_64_fastpath+0x1f/0x96
>>>>
>>>> Freed by task 1402:
>>>>    save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>>>>    set_track mm/kasan/kasan.c:459 [inline]
>>>>    kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
>>>>    __cache_free mm/slab.c:3492 [inline]
>>>>    kfree+0xca/0x250 mm/slab.c:3807
>>>>    irqfd_shutdown+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
>>>>    process_one_work+0xbfd/0x1bc0 kernel/workqueue.c:2113
>>>>    worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>>>>    kthread+0x37a/0x440 kernel/kthread.c:238
>>>>    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
>>>>
>>>> The buggy address belongs to the object at ffff8801cdf51000
>>>>    which belongs to the cache kmalloc-512 of size 512
>>>> The buggy address is located 384 bytes inside of
>>>>    512-byte region [ffff8801cdf51000, ffff8801cdf51200)
>>>> The buggy address belongs to the page:
>>>> page:00000000d08a0d63 count:1 mapcount:0 mapping:00000000d54c7be6 index:0x0
>>>> flags: 0x2fffc0000000100(slab)
>>>> raw: 02fffc0000000100 ffff8801cdf51000 0000000000000000 0000000100000006
>>>> raw: ffffea00073a7660 ffffea000737f3a0 ffff8801dac00940 0000000000000000
>>>> page dumped because: kasan: bad access detected
>>>>
>>>> Memory state around the buggy address:
>>>>    ffff8801cdf51080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>    ffff8801cdf51100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>> ffff8801cdf51180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>                      ^
>>>>    ffff8801cdf51200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>>    ffff8801cdf51280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>> ==================================================================
>>>>
> Tianyu, are you still planning to send a patch for this?  This is still
> happening.
>
> - Eric
Yes, I sent out fix patch and wait for review.
  https://patchwork.kernel.org/patch/10128925/