syzbot

 __vm_munmap+0x19b/0x390 mm/vma.c:2951
 __do_sys_munmap mm/mmap.c:1084 [inline]
 __se_sys_munmap mm/mmap.c:1081 [inline]
 __x64_sys_munmap+0x59/0x80 mm/mmap.c:1081
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
------------[ cut here ]------------
kernel BUG at mm/filemap.c:1499!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 5937 Comm: syz-executor137 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:folio_unlock mm/filemap.c:1499 [inline]
RIP: 0010:folio_unlock+0xb3/0xd0 mm/filemap.c:1494
Code: f3 68 ca ff 48 89 ef 31 f6 e8 e9 ed ff ff 5b 5d e9 e2 68 ca ff e8 dd 68 ca ff 48 c7 c6 00 8a 78 8b 48 89 ef e8 de c9 11 00 90 <0f> 0b 48 89 df e8 d3 83 2d 00 e9 7b ff ff ff 66 66 2e 0f 1f 84 00
RSP: 0018:ffffc9000359f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000359f830
RDX: ffff888027d14880 RSI: ffffffff81ef7612 RDI: ffff888027d14cc4
RBP: ffffea0000dfa680 R08: 0000000000000000 R09: fffffbfff20c49e2
R10: ffffffff90624f17 R11: 0000000000000003 R12: ffff888035b30890
R13: ffff888035b30bb0 R14: ffffea0000dfa680 R15: ffffc9000359fde8
FS:  0000555555b9a380(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5e877c6264 CR3: 0000000031914000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 netfs_perform_write+0xc04/0x2140 fs/netfs/buffered_write.c:400
 netfs_buffered_write_iter_locked fs/netfs/buffered_write.c:445 [inline]
 netfs_file_write_iter+0x494/0x550 fs/netfs/buffered_write.c:484
 v9fs_file_write_iter+0x9b/0x100 fs/9p/vfs_file.c:407
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:679
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5e87770829
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd7fd729d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffd7fd729f0 RCX: 00007f5e87770829
RDX: 000000000000000a RSI: 0000400000000080 RDI: 0000000000000004
RBP: 0000000000000001 R08: 00007ffd7fd72777 R09: 00000000000000a0
R10: 0000000000000001 R11: 0000000000000246 R12: 00007ffd7fd729ec
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:folio_unlock mm/filemap.c:1499 [inline]
RIP: 0010:folio_unlock+0xb3/0xd0 mm/filemap.c:1494
Code: f3 68 ca ff 48 89 ef 31 f6 e8 e9 ed ff ff 5b 5d e9 e2 68 ca ff e8 dd 68 ca ff 48 c7 c6 00 8a 78 8b 48 89 ef e8 de c9 11 00 90 <0f> 0b 48 89 df e8 d3 83 2d 00 e9 7b ff ff ff 66 66 2e 0f 1f 84 00
RSP: 0018:ffffc9000359f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000359f830
RDX: ffff888027d14880 RSI: ffffffff81ef7612 RDI: ffff888027d14cc4
RBP: ffffea0000dfa680 R08: 0000000000000000 R09: fffffbfff20c49e2
R10: ffffffff90624f17 R11: 0000000000000003 R12: ffff888035b30890
R13: ffff888035b30bb0 R14: ffffea0000dfa680 R15: ffffc9000359fde8
FS:  0000555555b9a380(0000) GS:ffff88806a600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005595a83ba0f8 CR3: 0000000031914000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400