WARNING in kvm_put_kvm (3)

Status: upstream: reported C repro on 2026/08/09 19:14
Subsystems: kvm
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+d4faf7db59e11f6fd1ab@syzkaller.appspotmail.com
Fix commit: srcu: Fix WARN_ON() for rcu_segcblist_n_cbs() in cleanup_srcu_struct()
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 48d, last: 1d00h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
c024d28d patching 💥 WARNING in kvm_put_kvm (3) 2026/08/12 14:23 2026/08/12 14:26 2026/08/12 14:58 a56bc0a5
e4ed1a8c assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING in kvm_put_kvm (3) 2026/08/09 01:24 2026/08/09 01:24 2026/08/09 02:29 5d63f80b
▶ ▼ Discussions (5)
Title Replies (including bot) Last reply
[PATCH 09/19] srcu: Fix WARN_ON() for rcu_segcblist_n_cbs() in cleanup_srcu_struct() 1 (1) 2026/09/19 00:35
[syzbot] [kvm?] WARNING in kvm_put_kvm (3) 1 (6) 2026/09/14 11:55
[PATCH v2] srcu: Fix WARN_ON() for rcu_segcblist_n_cbs() in cleanup_srcu_struct() 2 (2) 2026/09/01 17:39
[BUG] srcu: false-positive WARN in cleanup_srcu_struct() after 78a38cbf6f20 15 (15) 2026/08/29 23:08
[PATCH] srcu: Fix WARN_ON() for rcu_segcblist_n_cbs() in cleanup_srcu_struct() 2 (2) 2026/08/29 13:19
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in kvm_put_kvm (2) bcachefs -1 18 620d 701d 0/29 auto-obsoleted due to no activity on 2025/03/14 05:33
android-6-12 WARNING in kvm_put_kvm origin:downstream -1 syz, C 38585 381d 441d 0/1 auto-obsoleted due to no activity on 2025/10/29 15:36
upstream WARNING in kvm_put_kvm kvm -1 14 821d 830d 0/29 closed as invalid on 2024/08/16 18:20
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/08/24 03:57 46m shpark061104@gmail.com linux-next no crash job log log
2026/08/23 10:10 26m shpark061104@gmail.com patch git://git.kernel.org/pub/scm/virt/kvm/kvm.git master OK job log log
2026/08/23 09:33 26m shpark061104@gmail.com git://git.kernel.org/pub/scm/virt/kvm/kvm.git master no crash job log log
▶ ▼ Cause bisection attempts (2)
Created Duration User Patch Repo Result
2026/09/20 16:41 0m bisect linux-next error
2026/08/10 14:08 0m bisect linux-next error

Sample crash report:
------------[ cut here ]------------
timer_delete_sync(&sdp->delay_work) && rcu_segcblist_n_cbs(&sdp->srcu_cblist)
WARNING: kernel/rcu/srcutree.c:707 at cleanup_srcu_struct+0x3d6/0x8b0 kernel/rcu/srcutree.c:706, CPU#0: syz.0.4746/16077
Modules linked in:
CPU: 0 UID: 0 PID: 16077 Comm: syz.0.4746 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:cleanup_srcu_struct+0x3d6/0x8b0 kernel/rcu/srcutree.c:706
Code: fd 8b 00 48 83 7d 00 00 4c 8b 74 24 10 0f 85 dd 03 00 00 41 ff c5 41 83 e5 0f 41 83 fd 07 0f 86 e2 fe ff ff e9 ab 00 00 00 90 <0f> 0b 90 4c 8d b5 00 02 00 00 4c 89 f3 48 c1 eb 03 48 b8 00 00 00
RSP: 0018:ffffc90002e2fc10 EFLAGS: 00010206
RAX: 1ffffd1ffff8ff4d RBX: 0000607edafad980 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: ffffffff8e475f59 RDI: 00000000ffffffff
RBP: ffffe8ffffc7f980 R08: ffffffff907a2b7f R09: 1ffffffff20f456f
R10: dffffc0000000000 R11: fffffbfff20f4570 R12: ffff88802b081000
R13: 0000000000000000 R14: ffffe8ffffc7fa68 R15: 1ffffffff1ce91de
FS:  0000000000000000(0000) GS:ffff888124cd2000(0063) knlGS:0000000057310480
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000073e86000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 kvm_destroy_vm virt/kvm/kvm_main.c:1303 [inline]
 kvm_put_kvm+0x9cb/0xb50 virt/kvm/kvm_main.c:1332
 kvm_vm_release+0x43/0x50 virt/kvm/kvm_main.c:1355
 __fput+0x418/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 __do_fast_syscall_32+0x437/0x6a0 arch/x86/entry/syscall_32.c:294
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:316
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f470ec
Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 58 b8
RSP: 002b:00000000ffa0002c EFLAGS: 00000206 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000000001e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	85 d2                	test   %edx,%edx
   3:	74 0a                	je     0xf
   5:	89 ce                	mov    %ecx,%esi
   7:	81 e6 ff 0f 00 00    	and    $0xfff,%esi
   d:	89 32                	mov    %esi,(%rdx)
   f:	85 c0                	test   %eax,%eax
  11:	74 05                	je     0x18
  13:	c1 e9 0c             	shr    $0xc,%ecx
  16:	89 08                	mov    %ecx,(%rax)
  18:	31 c0                	xor    %eax,%eax
  1a:	5e                   	pop    %rsi
  1b:	5d                   	pop    %rbp
  1c:	c3                   	ret
  1d:	90                   	nop
  1e:	0f 1f 00             	nopl   (%rax)
  21:	51                   	push   %rcx
  22:	52                   	push   %rdx
  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                   	ret
  2e:	90                   	nop
  2f:	90                   	nop
  30:	90                   	nop
  31:	90                   	nop
  32:	90                   	nop
  33:	90                   	nop
  34:	90                   	nop
  35:	90                   	nop
  36:	90                   	nop
  37:	90                   	nop
  38:	90                   	nop
  39:	90                   	nop
  3a:	90                   	nop
  3b:	90                   	nop
  3c:	90                   	nop
  3d:	90                   	nop
  3e:	58                   	pop    %rax
  3f:	b8                   	.byte 0xb8

Crashes (26):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/14 07:03 upstream 50d05c7c76c9 70a60e12 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in kvm_put_kvm
2026/09/04 08:29 upstream 841e384b841a 801f0966 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in kvm_put_kvm
2026/08/08 23:50 linux-next 6b8c8af514d7 5d63f80b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/08 22:09 linux-next 6b8c8af514d7 5d63f80b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/08 20:33 linux-next 6b8c8af514d7 5d63f80b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/08 19:28 linux-next 6b8c8af514d7 5d63f80b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/08 15:12 linux-next 6b8c8af514d7 5d63f80b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/09/24 19:42 upstream 62f4c998b297 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in kvm_put_kvm
2026/09/02 16:16 upstream 89a312991dc6 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in kvm_put_kvm
2026/09/02 16:13 upstream 89a312991dc6 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in kvm_put_kvm
2026/09/02 16:11 upstream 89a312991dc6 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in kvm_put_kvm
2026/09/01 06:52 upstream bf1079577a11 316d9396 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in kvm_put_kvm
2026/08/27 06:50 upstream 73e3f0710014 a2b77b9e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in kvm_put_kvm
2026/09/14 03:06 upstream 50d05c7c76c9 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in kvm_put_kvm
2026/09/05 17:53 upstream 654ae5d73c05 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in kvm_put_kvm
2026/09/04 06:01 upstream 841e384b841a 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in kvm_put_kvm
2026/09/20 02:30 upstream 518e5b794c06 853b104b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in kvm_put_kvm
2026/09/23 11:21 upstream 50d05c7c76c9 abce1216 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in kvm_put_kvm
2026/08/23 19:05 linux-next 903c1cf6dff9 1e72964b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in kvm_put_kvm
2026/08/23 16:23 linux-next 903c1cf6dff9 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in kvm_put_kvm
2026/08/19 00:42 linux-next 5453bc3279e9 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in kvm_put_kvm
2026/08/14 20:04 linux-next 2697ef8943c9 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/11 03:45 linux-next 3d08ff75a47a 039457bd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/11 03:45 linux-next 3d08ff75a47a 039457bd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/10 10:29 linux-next 6b8c8af514d7 558388e4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
2026/08/08 11:54 linux-next 6b8c8af514d7 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in kvm_put_kvm
* Struck through repros no longer work on HEAD.