KASAN: slab-out-of-bounds Read in gfn_to_memslot

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 4f8a3cc1 Merge tag 'x86-urgent-2020-04-12' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=104b9407e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=3bfbde87e8e65624
dashboard link: https://syzkaller.appspot.com/bug?extid=2e0179e5185bcd5b9440
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13e78c7de00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14cf613fe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e0179...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in search_memslots include/linux/kvm_host.h:1051 [inline]
BUG: KASAN: slab-out-of-bounds in __gfn_to_memslot include/linux/kvm_host.h:1063 [inline]
BUG: KASAN: slab-out-of-bounds in gfn_to_memslot+0x275/0x470 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1597
Read of size 8 at addr ffff888097b31468 by task syz-executor165/9960

CPU: 0 PID: 9960 Comm: syz-executor165 Not tainted 5.6.0-syzkaller #0
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+0x1e9/0x30e lib/dump_stack.c:118
print_address_description+0x74/0x5c0 mm/kasan/report.c:382
__kasan_report+0x103/0x1a0 mm/kasan/report.c:511
kasan_report+0x4d/0x80 mm/kasan/common.c:625

Allocated by task 9966:
save_stack mm/kasan/common.c:49 [inline]
set_track mm/kasan/common.c:57 [inline]
__kasan_kmalloc+0x114/0x160 mm/kasan/common.c:495
kmalloc_node include/linux/slab.h:578 [inline]
kvmalloc_node+0x81/0x100 mm/util.c:574
kvmalloc include/linux/mm.h:757 [inline]
kvzalloc include/linux/mm.h:765 [inline]
kvm_dup_memslots arch/x86/kvm/../../../virt/kvm/kvm_main.c:1101 [inline]
kvm_set_memslot+0x124/0x15b0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1118
__kvm_set_memory_region+0x1388/0x16c0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1300
kvm_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1321 [inline]
kvm_vm_ioctl_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1333 [inline]
kvm_vm_ioctl+0x930/0x2530 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3604
vfs_ioctl fs/ioctl.c:47 [inline]
ksys_ioctl fs/ioctl.c:763 [inline]
__do_sys_ioctl fs/ioctl.c:772 [inline]
__se_sys_ioctl+0xf9/0x160 fs/ioctl.c:770
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 8700:
save_stack mm/kasan/common.c:49 [inline]
set_track mm/kasan/common.c:57 [inline]
kasan_set_free_info mm/kasan/common.c:317 [inline]
__kasan_slab_free+0x125/0x190 mm/kasan/common.c:456
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x220 mm/slab.c:3757
kvm_free_memslots arch/x86/kvm/../../../virt/kvm/kvm_main.c:601 [inline]
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:810 [inline]
kvm_put_kvm+0xa8d/0xcb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:828
kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:851
__fput+0x2ed/0x750 fs/file_table.c:280
task_work_run+0x147/0x1d0 kernel/task_work.c:123
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:165 [inline]
prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196
entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff888097b31000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1128 bytes inside of
2048-byte region [ffff888097b31000, ffff888097b31800)
The buggy address belongs to the page:
page:ffffea00025ecc40 refcount:1 mapcount:0 mapping:00000000499db978 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029ef288 ffffea0002a34408 ffff8880aa400e00
raw: 0000000000000000 ffff888097b31000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888097b31300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888097b31380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888097b31400: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
^
ffff888097b31480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888097b31500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[syzbot]

syzbot has bisected this bug to:

commit 36947254e5f981aeeedab1c7dfa35fc34d330e80
Author: Sean Christopherson <sean.j.chr...@intel.com>
Date: Tue Feb 18 21:07:32 2020 +0000

KVM: Dynamically size memslot array based on number of used slots

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1099775de00000
start commit: 4f8a3cc1 Merge tag 'x86-urgent-2020-04-12' of git://git.ke..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=1299775de00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1499775de00000

kernel config: https://syzkaller.appspot.com/x/.config?x=3bfbde87e8e65624
dashboard link: https://syzkaller.appspot.com/bug?extid=2e0179e5185bcd5b9440

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13e78c7de00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14cf613fe00000

Reported-by: syzbot+2e0179...@syzkaller.appspotmail.com
Fixes: 36947254e5f9 ("KVM: Dynamically size memslot array based on number of used slots")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Sean Christopherson]

#syz dup: KASAN: slab-out-of-bounds Read in __kvm_gfn_to_hva_cache_init