Date:   Sat, 26 May 2018 11:25:44 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+d8f8a4d784b336549b5b@...kaller.appspotmail.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>, KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: KASAN: slab-out-of-bounds Read in vmx_vcpu_run

#syz dup: KASAN: use-after-free Read in do_general_protection

On Sun, May 13, 2018 at 4:21 PM, syzbot
<syzbot+d8f8a4d784b336549b5b@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    036db8bd9637 Merge branch 'for-4.17-fixes' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11228e07800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=31f4b3733894ef79
> dashboard link: https://syzkaller.appspot.com/bug?extid=d8f8a4d784b336549b5b
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d8f8a4d784b336549b5b@...kaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in msr_write_intercepted
> arch/x86/kvm/vmx.c:2126 [inline]
> BUG: KASAN: slab-out-of-bounds in vmx_vcpu_run+0x2379/0x25f0
> arch/x86/kvm/vmx.c:9869
> Read of size 8 at addr ffff8801d3efc840 by task syz-executor1/11848
>
> CPU: 1 PID: 11848 Comm: syz-executor1 Not tainted 4.17.0-rc4+ #39
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> 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
>  msr_write_intercepted arch/x86/kvm/vmx.c:2126 [inline]
>  vmx_vcpu_run+0x2379/0x25f0 arch/x86/kvm/vmx.c:9869
>
> Allocated by task 11848:
>  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]
>  tcp_sendmsg_fastopen net/ipv4/tcp.c:1145 [inline]
>  tcp_sendmsg_locked+0x2ff7/0x3ee0 net/ipv4/tcp.c:1209
>  tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1447
>  inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
>  sock_sendmsg_nosec net/socket.c:629 [inline]
>  sock_sendmsg+0xd5/0x120 net/socket.c:639
>  __sys_sendto+0x3d7/0x670 net/socket.c:1789
>  __do_sys_sendto net/socket.c:1801 [inline]
>  __se_sys_sendto net/socket.c:1797 [inline]
>  __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1797
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 2388:
>  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
>  inotify_free_event+0x15/0x20 fs/notify/inotify/inotify_fsnotify.c:182
>  fsnotify_destroy_event.part.1+0x1a8/0x270 fs/notify/notification.c:87
>  fsnotify_destroy_event+0x69/0x80 fs/notify/notification.c:74
>  inotify_read+0x5a8/0x9b0 fs/notify/inotify/inotify_user.c:246
>  __vfs_read+0x10f/0xa50 fs/read_write.c:416
>  vfs_read+0x17f/0x3d0 fs/read_write.c:452
>  ksys_read+0xf9/0x250 fs/read_write.c:578
>  __do_sys_read fs/read_write.c:588 [inline]
>  __se_sys_read fs/read_write.c:586 [inline]
>  __x64_sys_read+0x73/0xb0 fs/read_write.c:586
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8801d3efc800
>  which belongs to the cache kmalloc-64 of size 64
> The buggy address is located 0 bytes to the right of
>  64-byte region [ffff8801d3efc800, ffff8801d3efc840)
> The buggy address belongs to the page:
> page:ffffea00074fbf00 count:1 mapcount:0 mapping:ffff8801d3efc000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801d3efc000 0000000000000000 0000000100000020
> raw: ffffea00076687a0 ffffea000766e660 ffff8801da800340 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801d3efc700: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff8801d3efc780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>>
>> ffff8801d3efc800: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>
>                                            ^
>  ffff8801d3efc880: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>  ffff8801d3efc900: fb fb fb fb fb fb fb fb 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:
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> syzbot.
>
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