Re: [syzbot] WARNING: kmalloc bug in kvm_page_track_create_memslot

[Paolo Bonzini]

#syz dup: WARNING: kmalloc bug in memslot_rmap_alloc

On 18/10/21 08:42, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    d999ade1cc86 Merge tag 'perf-tools-fixes-for-v5.15-2021-10..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=161ab644b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bab9d35f204746a7
> dashboard link: https://syzkaller.appspot.com/bug?extid=d9c9b7cff3d4ec7a589e
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11fcdc34b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14785d34b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d9c9b7cff3d4ec7a589e@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> 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.
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 6533 at mm/util.c:597 kvmalloc_node+0x111/0x120 mm/util.c:597
> Modules linked in:
> CPU: 0 PID: 6533 Comm: syz-executor711 Not tainted 5.15.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:kvmalloc_node+0x111/0x120 mm/util.c:597
> Code: 01 00 00 00 4c 89 e7 e8 ad 18 0d 00 49 89 c5 e9 69 ff ff ff e8 60 91 d0 ff 41 89 ed 41 81 cd 00 20 01 00 eb 95 e8 4f 91 d0 ff <0f> 0b e9 4c ff ff ff 0f 1f 84 00 00 00 00 00 55 48 89 fd 53 e8 36
> RSP: 0018:ffffc900011ef6e8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff88807a7e8000 RSI: ffffffff81a646c1 RDI: 0000000000000003
> RBP: 0000000000400dc0 R08: 000000007fffffff R09: ffff8880b9d32a0b
> R10: ffffffff81a6467e R11: 000000000000003f R12: 00000000e0000000
> R13: 0000000000000000 R14: 00000000ffffffff R15: ffffc900011ef950
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0063) knlGS:0000000056d512c0
> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> CR2: 000055ad809529a0 CR3: 000000001ae94000 CR4: 00000000003526e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   kvmalloc include/linux/mm.h:805 [inline]
>   kvmalloc_array include/linux/mm.h:823 [inline]
>   kvcalloc include/linux/mm.h:828 [inline]
>   kvm_page_track_create_memslot+0x50/0x110 arch/x86/kvm/mmu/page_track.c:39
>   kvm_alloc_memslot_metadata arch/x86/kvm/x86.c:11501 [inline]
>   kvm_arch_prepare_memory_region+0x350/0x610 arch/x86/kvm/x86.c:11538
>   kvm_set_memslot+0x172/0x1a40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1592
>   __kvm_set_memory_region+0xc1c/0x13d0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1755
>   kvm_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1776 [inline]
>   kvm_vm_ioctl_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1788 [inline]
>   kvm_vm_ioctl+0x520/0x23d0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4363
>   kvm_vm_compat_ioctl+0x288/0x350 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4588
>   __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:972
>   do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
>   __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
>   do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
>   entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> RIP: 0023:0xf7e67549
> Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000ff89659c EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000004020ae46
> RDX: 00000000200001c0 RSI: 00000000ff8965f0 RDI: 00000000f7f0a000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> ----------------
> Code disassembly (best guess):
>     0:	03 74 c0 01          	add    0x1(%rax,%rax,8),%esi
>     4:	10 05 03 74 b8 01    	adc    %al,0x1b87403(%rip)        # 0x1b8740d
>     a:	10 06                	adc    %al,(%rsi)
>     c:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
>    10:	10 07                	adc    %al,(%rdi)
>    12:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
>    16:	10 08                	adc    %cl,(%rax)
>    18:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
>    1c:	00 00                	add    %al,(%rax)
>    1e:	00 00                	add    %al,(%rax)
>    20:	00 51 52             	add    %dl,0x52(%rcx)
>    23:	55                   	push   %rbp
>    24:	89 e5                	mov    %esp,%ebp
>    26:	0f 34                	sysenter
>    28:	cd 80                	int    $0x80
> * 2a:	5d                   	pop    %rbp <-- trapping instruction
>    2b:	5a                   	pop    %rdx
>    2c:	59                   	pop    %rcx
>    2d:	c3                   	retq
>    2e:	90                   	nop
>    2f:	90                   	nop
>    30:	90                   	nop
>    31:	90                   	nop
>    32:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
>    39:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
>
>
> ---
> This report 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@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches