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Date:   Wed, 02 Jan 2019 03:11:04 -0800
From:   syzbot <syzbot+028366e52c9ace67deb3@...kaller.appspotmail.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: KASAN: slab-out-of-bounds Read in kvm_clear_dirty_log_protect

Hello,

syzbot found the following crash on:

HEAD commit:    f12e840c819b Merge branch 'for-linus' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b03ee7400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=76d28549be7c27cf
dashboard link: https://syzkaller.appspot.com/bug?extid=028366e52c9ace67deb3
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104dc120c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1656b6e7400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+028366e52c9ace67deb3@...kaller.appspotmail.com

audit: type=1800 audit(1546340268.292:30): pid=7481 uid=0 auid=4294967295  
ses=4294967295 subj==unconfined op=collect_data cause=failed(directio)  
comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0
IPVS: ftp: loaded support on port[0] = 21
L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and  
https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html for details.
==================================================================
BUG: KASAN: slab-out-of-bounds in kvm_clear_dirty_log_protect+0x8cf/0x970  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1262
Read of size 8 at addr ffff88809e631290 by task syz-executor007/7635

CPU: 0 PID: 7635 Comm: syz-executor007 Not tainted 4.20.0+ #2
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+0x1db/0x2d0 lib/dump_stack.c:113
  print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
  kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
  kvm_clear_dirty_log_protect+0x8cf/0x970  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1262
  kvm_vm_ioctl_clear_dirty_log+0xff/0x260 arch/x86/kvm/x86.c:4468
  kvm_vm_ioctl+0xc19/0x1fe0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3127
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:509 [inline]
  do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
  ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
  __do_sys_ioctl fs/ioctl.c:720 [inline]
  __se_sys_ioctl fs/ioctl.c:718 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440b09
Code: 23 02 00 85 c0 b8 00 00 00 00 48 0f 44 c3 5b c3 90 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 0b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00000000007dff68 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004a28d8 RCX: 0000000000440b09
RDX: 0000000020000080 RSI: 00000000c018aec0 RDI: 0000000000000004
RBP: 00000000004a28d8 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000120080522 R11: 0000000000000217 R12: 00000000004022a0
R13: 0000000000402330 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7635:
  save_stack+0x45/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  kasan_kmalloc mm/kasan/common.c:482 [inline]
  kasan_kmalloc+0xcf/0xe0 mm/kasan/common.c:455
  __do_kmalloc_node mm/slab.c:3671 [inline]
  __kmalloc_node+0x4e/0x70 mm/slab.c:3678
  kmalloc_node include/linux/slab.h:588 [inline]
  kvmalloc_node+0x68/0x100 mm/util.c:416
  kvmalloc include/linux/mm.h:602 [inline]
  kvzalloc include/linux/mm.h:610 [inline]
  kvm_create_dirty_bitmap arch/x86/kvm/../../../virt/kvm/kvm_main.c:792  
[inline]
  __kvm_set_memory_region+0x1da1/0x2c40  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1018
  kvm_set_memory_region+0x2f/0x60  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1084
  kvm_vm_ioctl_set_memory_region  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1096 [inline]
  kvm_vm_ioctl+0xafa/0x1fe0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3108
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:509 [inline]
  do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
  ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
  __do_sys_ioctl fs/ioctl.c:720 [inline]
  __se_sys_ioctl fs/ioctl.c:718 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4427:
  save_stack+0x45/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
  kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
  __cache_free mm/slab.c:3485 [inline]
  kfree+0xcf/0x230 mm/slab.c:3804
  single_release+0x95/0xc0 fs/seq_file.c:597
  __fput+0x3c5/0xb10 fs/file_table.c:278
  ____fput+0x16/0x20 fs/file_table.c:309
  task_work_run+0x1f4/0x2b0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x32a/0x3b0 arch/x86/entry/common.c:166
  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
  do_syscall_64+0x696/0x800 arch/x86/entry/common.c:293
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88809e631280
  which belongs to the cache kmalloc-32 of size 32
The buggy address is located 16 bytes inside of
  32-byte region [ffff88809e631280, ffff88809e6312a0)
The buggy address belongs to the page:
page:ffffea0002798c40 count:1 mapcount:0 mapping:ffff88812c3f01c0  
index:0xffff88809e631fc1
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002763388 ffff88812c3f1238 ffff88812c3f01c0
raw: ffff88809e631fc1 ffff88809e631000 000000010000001c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88809e631180: 00 01 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
  ffff88809e631200: fb fb fb fb fc fc fc fc 04 fc fc fc fc fc fc fc
> ffff88809e631280: 00 00 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
                          ^
  ffff88809e631300: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
  ffff88809e631380: fb fb fb fb fc fc fc fc fb fb fb fb 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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