linux-kernel - Re: [syzbot] [kvm?] WARNING in kvm_gmem_fault_user

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Message-ID: <697ee733.050a0220.1d0a41.0014.GAE@google.com>
Date: Sat, 31 Jan 2026 21:40:03 -0800
From: syzbot <syzbot+33a04338019ac7e43a44@...kaller.appspotmail.com>
To: kartikey406@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [kvm?] WARNING in kvm_gmem_fault_user_mapping

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in kvm_gmem_fault_user_mapping

------------[ cut here ]------------
folio_test_large(folio)
WARNING: arch/x86/kvm/../../../virt/kvm/guest_memfd.c:416 at kvm_gmem_fault_user_mapping+0x4b5/0x6e0 virt/kvm/guest_memfd.c:416, CPU#1: syz.3.91/7037
Modules linked in:
CPU: 1 UID: 0 PID: 7037 Comm: syz.3.91 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:kvm_gmem_fault_user_mapping+0x4b5/0x6e0 virt/kvm/guest_memfd.c:416
Code: 00 e9 a1 fe ff ff bd 00 04 00 00 eb d9 e8 43 b8 83 00 48 c7 c6 e0 9f 82 8b 48 89 df e8 54 fb ce 00 90 0f 0b e8 2c b8 83 00 90 <0f> 0b 90 48 8d 6b 34 48 89 df e8 ec f6 bb 00 be 04 00 00 00 48 89
RSP: 0018:ffffc90004477848 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffea0001c10000 RCX: ffffffff81834070
RDX: ffff88802e784980 RSI: ffffffff81834334 RDI: ffff88802e784980
RBP: ffffc900044779f8 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000040 R11: 0000000000000000 R12: ffffea0001c10000
R13: ffffc90004477a08 R14: 0000000000000040 R15: ffffea0001c10008
FS:  00007f25057f76c0(0000) GS:ffff8881246d9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6a111b7d58 CR3: 00000000310af000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __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: 0033:0x7f250499aeb9
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:00007f25057f7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000095
RAX: ffffffffffffffda RBX: 00007f2504c15fa0 RCX: 00007f250499aeb9
RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000000000
RBP: 00007f2504a08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2504c16038 R14: 00007f2504c15fa0 R15: 00007ffc912316c8
 </TASK>


Tested on:

commit:         162b4244 Merge tag 'iommu-fixes-v6.19-rc7' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d7053a580000
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=1048d322580000