KASAN: use-after-free Read in kvm_write_guest_offset_cached

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 442b8cea2477 Add linux-next specific files for 20181109
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=174d326d400000
kernel config: https://syzkaller.appspot.com/x/.config?x=2f72bdb11df9fbe8
dashboard link: https://syzkaller.appspot.com/bug?extid=ff40b9bc4835ea83211c
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14f5df7b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ff40b9...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in mark_page_dirty_in_slot
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2056 [inline]
BUG: KASAN: use-after-free in kvm_write_guest_offset_cached+0x693/0x6b0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1988
Read of size 8 at addr ffff8801b9363778 by task syz-executor1/30438

CPU: 1 PID: 30438 Comm: syz-executor1 Not tainted 4.20.0-rc1-next-20181109+
#110
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
mark_page_dirty_in_slot arch/x86/kvm/../../../virt/kvm/kvm_main.c:2056
[inline]
kvm_write_guest_offset_cached+0x693/0x6b0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1988
kvm_steal_time_set_preempted arch/x86/kvm/x86.c:3241 [inline]
kvm_arch_vcpu_put+0x365/0x420 arch/x86/kvm/x86.c:3268
kvm_sched_out+0x91/0xb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3993
__fire_sched_out_preempt_notifiers kernel/sched/core.c:2503 [inline]
fire_sched_out_preempt_notifiers kernel/sched/core.c:2511 [inline]
prepare_task_switch kernel/sched/core.c:2617 [inline]
context_switch kernel/sched/core.c:2796 [inline]
__schedule+0x11ca/0x21d0 kernel/sched/core.c:3472
preempt_schedule_irq+0xb9/0x140 kernel/sched/core.c:3699
retint_kernel+0x1b/0x2d
RIP: 0010:search_memslots include/linux/kvm_host.h:955 [inline]
RIP: 0010:__gfn_to_memslot include/linux/kvm_host.h:976 [inline]
RIP: 0010:__kvm_gfn_to_hva_cache_init+0x2ed/0xd10
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1935
Code: 3c 02 00 0f 85 0d 0a 00 00 4d 03 6c 24 08 48 89 df 4c 89 ee e8 04 16
78 00 4c 39 eb 0f 82 6e 01 00 00 45 31 ed e8 43 15 78 00 <44> 89 fe 44 89
ef e8 c8 15 78 00 45 39 fd 0f 8d cf 00 00 00 e8 2a
RSP: 0018:ffff8801cbfee970 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
RAX: ffff8801b9a4c280 RBX: 0000000000000000 RCX: ffffffff8107942f
RDX: 0000000000000000 RSI: ffffffff8107936d RDI: 0000000000000006
RBP: ffff8801cbfeeb60 R08: ffff8801b9a4c280 R09: ffffed00342bb209
R10: ffffed00342bb209 R11: ffff8801a15d904b R12: 0000000000000017
R13: 0000000000000017 R14: 0000000000000016 R15: 0000000000000017
kvm_gfn_to_hva_cache_init+0x15a/0x340
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1963
kvm_set_msr_common+0x1a0c/0x2670 arch/x86/kvm/x86.c:2549
vmx_set_msr+0x759/0x1f90 arch/x86/kvm/vmx.c:4360
kvm_set_msr+0x18a/0x370 arch/x86/kvm/x86.c:1324
do_set_msr+0x10d/0x1a0 arch/x86/kvm/x86.c:1353
__msr_io arch/x86/kvm/x86.c:2905 [inline]
msr_io+0x222/0x380 arch/x86/kvm/x86.c:2941
kvm_arch_vcpu_ioctl+0x961/0x3b00 arch/x86/kvm/x86.c:3956
kvm_vcpu_ioctl+0x278/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2748
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 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+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc292e62c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000020000280 RSI: 000000004008ae89 RDI: 0000000000000005
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc292e636d4
R13: 00000000004bff9d R14: 00000000004d0970 R15: 00000000ffffffff

Allocated by task 30427:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
__do_kmalloc_node mm/slab.c:3684 [inline]
__kmalloc_node+0x50/0x70 mm/slab.c:3691
kmalloc_node include/linux/slab.h:589 [inline]
kvmalloc_node+0xb9/0xf0 mm/util.c:416
kvmalloc include/linux/mm.h:577 [inline]
kvzalloc include/linux/mm.h:585 [inline]
__kvm_set_memory_region+0x116e/0x2d50
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1023
kvm_set_memory_region+0x2e/0x50
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1085
kvm_vm_ioctl_set_memory_region
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1097 [inline]
kvm_vm_ioctl+0x652/0x1d60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2995
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 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+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 30427:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
kvfree+0x61/0x70 mm/util.c:445
__kvm_set_memory_region+0x1cb3/0x2d50
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1067
kvm_set_memory_region+0x2e/0x50
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1085
kvm_vm_ioctl_set_memory_region
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1097 [inline]
kvm_vm_ioctl+0x652/0x1d60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2995
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 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+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801b9363080
which belongs to the cache kmalloc-64k of size 65536
The buggy address is located 1784 bytes inside of
65536-byte region [ffff8801b9363080, ffff8801b9373080)
The buggy address belongs to the page:
page:ffffea0006e4d800 count:1 mapcount:0 mapping:ffff8801da802500 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea0006906808 ffffea0007034808 ffff8801da802500
raw: 0000000000000000 ffff8801b9363080 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801b9363600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b9363680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801b9363700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801b9363780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b9363800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Wanpeng Li]

On Tue, 27 Nov 2018 at 12:51, syzbot
<syzbot+ff40b9...@syzkaller.appspotmail.com> wrote:
>
> Hello,

Is there beauty C codes?

Regards,
Wanpeng Li

[Dmitry Vyukov]

On Tue, Nov 27, 2018 at 7:14 AM, Wanpeng Li <kern...@gmail.com> wrote:
>
> On Tue, 27 Nov 2018 at 12:51, syzbot
> <syzbot+ff40b9...@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
>
> Is there beauty C codes?

syzbot does not have code like:

if (rand() % 2)
send_C_repro();

:)

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[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.