------------[ cut here ]------------
anon_vma->num_active_vmas
WARNING: mm/rmap.c:528 at unlink_anon_vmas+0x64e/0x8e0 mm/rmap.c:528, CPU#1: syz.5.6254/25287
Modules linked in:
CPU: 1 UID: 0 PID: 25287 Comm: syz.5.6254 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:unlink_anon_vmas+0x64e/0x8e0 mm/rmap.c:528
Code: 8b 40 30 48 39 c3 0f 85 9c 00 00 00 e8 9b 24 a7 ff 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc e8 83 24 a7 ff 90 <0f> 0b 90 e9 2e ff ff ff e8 75 24 a7 ff 90 0f 0b 90 e9 e0 fe ff ff
RSP: 0018:ffffc900060af758 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88804b2432a0 RCX: ffffffff82618da7
RDX: ffff888058f924c0 RSI: ffffffff82618e7d RDI: ffff888058f924c0
RBP: ffff8880364e9540 R08: 0000000000000007 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000000 R12: dffffc0000000000
R13: ffff888038fd6ca0 R14: ffff88804b2432b0 R15: ffff888038fd6cb0
FS:  0000000000000000(0000) GS:ffff8880d6445000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32963fff CR3: 000000000e598000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 free_pgtables+0x2e7/0xd80 mm/memory.c:427
 exit_mmap+0x44c/0xa30 mm/mmap.c:1314
 __mmput+0x12a/0x410 kernel/fork.c:1174
 mmput+0x67/0x80 kernel/fork.c:1197
 exit_mm kernel/exit.c:581 [inline]
 do_exit+0x78a/0x2aa0 kernel/exit.c:959
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1112
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x67c/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f265779c799
Code: Unable to access opcode bytes at 0x7f265779c76f.
RSP: 002b:00007f26586cd0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007f2657a15fa8 RCX: 00007f265779c799
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f2657a15fac
RBP: 00007f2657a15fa0 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2657a16038 R14: 00007ffcb25e7fe0 R15: 00007ffcb25e80c8
 </TASK>