Re: [syzbot] [kvm?] WARNING in kvm_gmem_fault_user_mapping

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in filemap_remove_folio

------------[ cut here ]------------
kernel BUG at mm/filemap.c:254!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 7475 Comm: syz.2.329 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:filemap_remove_folio+0x20f/0x270 mm/filemap.c:254
Code: fc 00 10 00 00 0f 86 5f ff ff ff eb 9e e8 b9 e5 c6 ff 48 c7 c6 20 0d 9d 8b 48 89 df e8 6a 2a 12 00 90 0f 0b e8 a2 e5 c6 ff 90 <0f> 0b e8 9a 38 31 00 e9 39 fe ff ff e8 90 38 31 00 e9 0c fe ff ff
RSP: 0018:ffffc9000caaf7f0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffea0001400000 RCX: ffffffff8240149d
RDX: ffff88802bcaa4c0 RSI: ffffffff824015fe RDI: ffff88802bcaa4c0
RBP: ffff88806b3047b0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88806b3045c0 R14: 0000000000000000 R15: 1000200001ee0000
FS:  00007fa5c3e506c0(0000) GS:ffff8881246d9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000572cf000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 kvm_gmem_get_folio+0x118/0x320 virt/kvm/guest_memfd.c:166
 kvm_gmem_fault_user_mapping+0x151/0x6e0 virt/kvm/guest_memfd.c:425
 __do_fault+0x10d/0x550 mm/memory.c:5323
 do_read_fault mm/memory.c:5758 [inline]
 do_fault+0xaf9/0x1990 mm/memory.c:5892
 do_pte_missing mm/memory.c:4404 [inline]
 handle_pte_fault mm/memory.c:6276 [inline]
 __handle_mm_fault+0x1807/0x2b50 mm/memory.c:6414
 handle_mm_fault+0x36d/0xa20 mm/memory.c:6583
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0xf9c/0x34d0 mm/gup.c:1428
 populate_vma_page_range+0x267/0x3f0 mm/gup.c:1860
 __mm_populate+0x107/0x3a0 mm/gup.c:1963
 do_mlock+0x3f0/0x7f0 mm/mlock.c:653
 __do_sys_mlock mm/mlock.c:661 [inline]
 __se_sys_mlock mm/mlock.c:659 [inline]
 __x64_sys_mlock+0x59/0x80 mm/mlock.c:659
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa5c2f9aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa5c3e50028 EFLAGS: 00000246 ORIG_RAX: 0000000000000095
RAX: ffffffffffffffda RBX: 00007fa5c3215fa0 RCX: 00007fa5c2f9aeb9
RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000000000
RBP: 00007fa5c3008c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5c3216038 R14: 00007fa5c3215fa0 R15: 00007fff2603f848
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:filemap_remove_folio+0x20f/0x270 mm/filemap.c:254
Code: fc 00 10 00 00 0f 86 5f ff ff ff eb 9e e8 b9 e5 c6 ff 48 c7 c6 20 0d 9d 8b 48 89 df e8 6a 2a 12 00 90 0f 0b e8 a2 e5 c6 ff 90 <0f> 0b e8 9a 38 31 00 e9 39 fe ff ff e8 90 38 31 00 e9 0c fe ff ff
RSP: 0018:ffffc9000caaf7f0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffea0001400000 RCX: ffffffff8240149d
RDX: ffff88802bcaa4c0 RSI: ffffffff824015fe RDI: ffff88802bcaa4c0
RBP: ffff88806b3047b0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88806b3045c0 R14: 0000000000000000 R15: 1000200001ee0000
FS:  00007fa5c3e506c0(0000) GS:ffff8881245d9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000572cf000 CR4: 00000000003526f0


Tested on:

commit:         18f7fcd5 Linux 6.19-rc8
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e73322580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f1fac0919970b671
dashboard link: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17ca453a580000