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SubjectKASAN: slab-out-of-bounds Read in __kvm_map_gfn
From
Hello,

syzbot found the following crash on:

HEAD commit: bef7b2a7 Merge tag 'devicetree-for-5.7' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12672c5de00000
kernel config: https://syzkaller.appspot.com/x/.config?x=91b674b8f0368e69
dashboard link: https://syzkaller.appspot.com/bug?extid=516667c144d77aa5ba3c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1217010be00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=106c8febe00000

The bug was bisected to:

commit 3a00e7c47c382b30524e78b36ab047c16b8fcfef
Author: Alex Shi <alex.shi@linux.alibaba.com>
Date: Tue Jan 21 08:34:05 2020 +0000

ida: remove abandoned macros

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11c1efdbe00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=13c1efdbe00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15c1efdbe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+516667c144d77aa5ba3c@syzkaller.appspotmail.com
Fixes: 3a00e7c47c38 ("ida: remove abandoned macros")

L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
==================================================================
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 __kvm_map_gfn+0x933/0xa10 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2060
Read of size 8 at addr ffff88808e20b468 by task syz-executor368/7090

CPU: 0 PID: 7090 Comm: syz-executor368 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+0x188/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
__kasan_report.cold+0x35/0x4d mm/kasan/report.c:503
kasan_report+0x33/0x50 mm/kasan/common.c:648
search_memslots include/linux/kvm_host.h:1051 [inline]
__gfn_to_memslot include/linux/kvm_host.h:1063 [inline]
__kvm_map_gfn+0x933/0xa10 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2060
kvm_steal_time_set_preempted arch/x86/kvm/x86.c:3609 [inline]
kvm_arch_vcpu_put+0x3b9/0x530 arch/x86/kvm/x86.c:3642
vcpu_put+0x1b/0x70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:220
kvm_arch_vcpu_ioctl+0x1ae/0x2c20 arch/x86/kvm/x86.c:4620
kvm_vcpu_ioctl+0x866/0xe60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3291
kvm_vcpu_compat_ioctl+0x1ab/0x350 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3334
__do_compat_sys_ioctl fs/ioctl.c:857 [inline]
__se_compat_sys_ioctl fs/ioctl.c:808 [inline]
__ia32_compat_sys_ioctl+0x23d/0x2b0 fs/ioctl.c:808
do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Allocated by task 7090:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:518 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:491
kmalloc_node include/linux/slab.h:578 [inline]
kvmalloc_node+0x61/0xf0 mm/util.c:574
kvmalloc include/linux/mm.h:733 [inline]
kvzalloc include/linux/mm.h:741 [inline]
kvm_dup_memslots arch/x86/kvm/../../../virt/kvm/kvm_main.c:1101 [inline]
kvm_set_memslot+0x115/0x1530 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1118
__kvm_set_memory_region+0xcf7/0x1320 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1300
__x86_set_memory_region+0x2a3/0x5a0 arch/x86/kvm/x86.c:9845
alloc_apic_access_page arch/x86/kvm/vmx/vmx.c:3544 [inline]
vmx_create_vcpu+0x2107/0x2b40 arch/x86/kvm/vmx/vmx.c:6772
kvm_arch_vcpu_create+0x6ef/0xb80 arch/x86/kvm/x86.c:9365
kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3030 [inline]
kvm_vm_ioctl+0x15f7/0x23e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3585
kvm_vm_compat_ioctl+0x125/0x240 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3798
__do_compat_sys_ioctl fs/ioctl.c:857 [inline]
__se_compat_sys_ioctl fs/ioctl.c:808 [inline]
__ia32_compat_sys_ioctl+0x23d/0x2b0 fs/ioctl.c:808
do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff88808e20b000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1128 bytes inside of
2048-byte region [ffff88808e20b000, ffff88808e20b800)
The buggy address belongs to the page:
page:ffffea00023882c0 refcount:1 mapcount:0 mapping:00000000044fe846 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00027cbcc8 ffffea0002591e08 ffff8880aa000e00
raw: 0000000000000000 ffff88808e20b000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808e20b300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88808e20b380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88808e20b400: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
^
ffff88808e20b480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88808e20b500: fc fc fc fc fc fc fc fc fc fc fc fc 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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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