linux-kernel - Re: KASAN: use-after-free Read in irq_bypass_unregister

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Date:   Sat, 26 May 2018 11:21:53 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+37364ced0d0b0fdf115c@...kaller.appspotmail.com>
Cc:     KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in irq_bypass_unregister_consumer

#syz dup: KASAN: use-after-free Write in irq_bypass_register_consumer

On Mon, May 21, 2018 at 7:25 PM, syzbot
<syzbot+37364ced0d0b0fdf115c@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    0b449a441dac Merge tag 'dmaengine-fix-4.17-rc6' of git://g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16a44b37800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f3b4e30da84ec1ed
> dashboard link: https://syzkaller.appspot.com/bug?extid=37364ced0d0b0fdf115c
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1120eb37800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f1227b800000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+37364ced0d0b0fdf115c@...kaller.appspotmail.com
>
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> IPVS: ftp: loaded support on port[0] = 21
> ==================================================================
> BUG: KASAN: use-after-free in irq_bypass_unregister_consumer+0x3cd/0x4a0
> virt/lib/irqbypass.c:247
> Read of size 8 at addr ffff8801adf2a168 by task kworker/0:1/24
>
> CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.17.0-rc5+ #59
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: kvm-irqfd-cleanup irqfd_shutdown
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  irq_bypass_unregister_consumer+0x3cd/0x4a0 virt/lib/irqbypass.c:247
>  irqfd_shutdown+0x112/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:145
>  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
>  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
>  kthread+0x345/0x410 kernel/kthread.c:240
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> Allocated by task 4534:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
>  kmalloc include/linux/slab.h:512 [inline]
>  kzalloc include/linux/slab.h:701 [inline]
>  kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
>  kvm_irqfd+0x187/0x1ec0 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
>  kvm_vm_ioctl+0xf84/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2997
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  file_ioctl fs/ioctl.c:500 [inline]
>  do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
>  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
>  __do_sys_ioctl fs/ioctl.c:708 [inline]
>  __se_sys_ioctl fs/ioctl.c:706 [inline]
>  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 24:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3813
>  irqfd_shutdown+0x13a/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
>  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
>  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
>  kthread+0x345/0x410 kernel/kthread.c:240
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> The buggy address belongs to the object at ffff8801adf2a000
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 360 bytes inside of
>  512-byte region [ffff8801adf2a000, ffff8801adf2a200)
> The buggy address belongs to the page:
> page:ffffea0006b7ca80 count:1 mapcount:0 mapping:ffff8801adf2a000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801adf2a000 0000000000000000 0000000100000006
> raw: ffffea0007647a20 ffffea0006b45ba0 ffff8801da800940 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801adf2a000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801adf2a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801adf2a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                                                           ^
>  ffff8801adf2a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801adf2a200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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