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

[syzbot <syzbot+2e0179e5185bcd5b9440@syzkaller.appspotmail.com>]

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+2e0179e5185bcd5b9440@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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