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SubjectKASAN: slab-out-of-bounds Read in kvm_clear_dirty_log_protect
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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@syzkaller.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.
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syzbot.
syzbot can test patches for this bug, for details see:
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