On Mon, Jun 17, 2024, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 2ccbdf43d5e7 Merge tag 'for-linus' of git://git.kernel.org.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1695b7ee980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b8786f381e62940f > dashboard link: https://syzkaller.appspot.com/bug?extid=d8775ae2dbebe5ab16fd > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/a4edf8b28d7f/disk-2ccbdf43.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/5f9b0fd6168d/vmlinux-2ccbdf43.xz > kernel image: https://storage.googleapis.com/syzbot-assets/a2c5f918ca4f/bzImage-2ccbdf43.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+d8775ae2dbebe5ab16fd@xxxxxxxxxxxxxxxxxxxxxxxxx > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 17017 at kernel/rcu/srcutree.c:653 cleanup_srcu_struct+0x37c/0x520 kernel/rcu/srcutree.c:653 > Modules linked in: > CPU: 0 PID: 17017 Comm: syz-executor.4 Not tainted 6.10.0-rc3-syzkaller-00044-g2ccbdf43d5e7 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 > RIP: 0010:cleanup_srcu_struct+0x37c/0x520 kernel/rcu/srcutree.c:653 > Code: 83 c4 20 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 90 0f 0b 90 48 83 c4 20 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 90 <0f> 0b 90 e9 35 ff ff ff 90 0f 0b 90 48 b8 00 00 00 00 00 fc ff df > RSP: 0018:ffffc90003567d20 EFLAGS: 00010202 > RAX: 0000000000000001 RBX: ffffc90002d6e000 RCX: 0000000000000002 > RDX: fffff91ffffab294 RSI: 0000000000000008 RDI: ffffe8ffffd59498 > RBP: ffff88805b6c0000 R08: 0000000000000000 R09: fffff91ffffab293 > R10: ffffe8ffffd5949f R11: 0000000000000000 R12: ffffc90002d778a8 > R13: ffffc90002d77880 R14: ffffc90002d77868 R15: 0000000000000004 > FS: 00007fa719dec6c0(0000) GS:ffff8880b9200000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020078000 CR3: 000000006176a000 CR4: 00000000003526f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1351 [inline] > kvm_put_kvm+0x8df/0xb80 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1380 > kvm_vm_release+0x42/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1403 > __fput+0x408/0xbb0 fs/file_table.c:422 > task_work_run+0x14e/0x250 kernel/task_work.c:180 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218 > do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x77/0x7f syzbot reported a rash of KVM cleanup_srcu_struct() splats, and while they suggest that KVM has a rogue SRCU reader, I strongly suspect that something is/was going sideways with bcachefs, and KVM is an innocent bystander. All of the splats have bcachefs activity shortly before the failure, and syzbot has never managed to find a reproducer. If if KVM were at fault, e.g. was accessing SRCU after its freed, I would expect at least one report to not include bcachefs activity, and I would think we'd have at least one reproducer. Furthermore, except for the __timer_delete_sync() splat, all of the issues mysteriously stopped occuring at roughly the same time, and I definitely don't recall fixing anything remotely relevant in KVM. So, I'm going to close all of the stale reports as invalid, and assign the __timer_delete_sync() to bcachefs, because again there's nothing in there that suggests KVM is at fault. general protection fault in detach_if_pending (3) bcachefs kvm 5 52d 52d general protection fault in get_work_pool (2) kvm 5 59d 59d WARNING in kvm_put_kvm kvm 14 51d 60d KASAN: wild-memory-access Read in __timer_delete_sync kvm 5 14d 81d <= ??? WARNING in srcu_check_nmi_safety kvm 255 51d 104d WARNING in cleanup_srcu_struct (4) kvm bcachefs 3567 51d 105d #syz invalid
