GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P24663/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=156137, q=486 ncpus=2)
task:syz.7.4524 state:R running task stack:22272 pid:24663 tgid:24657 ppid:22871 task_flags:0x20400040 flags:0x00080001
Call Trace:
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7256
irqentry_exit+0x6f/0x90 kernel/entry/common.c:211
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:unwind_get_return_address+0x3b/0x90 arch/x86/kernel/unwind_orc.c:369
Code: 00 00 fc ff df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 4c 83 3b 00 74 3a 48 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 <74> 08 48 89 df e8 4b cd b1 00 48 8b 3b e8 23 d0 18 00 85 c0 74 14
RSP: 0018:ffffc9000394ea08 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc9000394ea70 RCX: 0ee67a93d8fd4600
RDX: 0000000000000001 RSI: ffffffff8d6f9a62 RDI: ffffc9000394ea28
RBP: ffffc9000394eab0 R08: ffffc9000394fe10 R09: 0000000000000000
R10: ffffc9000394ea78 R11: fffff52000729d51 R12: ffff888025a29e40
R13: 0000000000000020 R14: dffffc0000000000 R15: 1ffff92000729d4e
arch_stack_walk+0xfc/0x150 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
kasan_kmalloc include/linux/kasan.h:262 [inline]
__kmalloc_cache_noprof+0x3d5/0x6f0 mm/slub.c:5725
kmalloc_noprof include/linux/slab.h:957 [inline]
slab_free_hook mm/slub.c:2467 [inline]
slab_free mm/slub.c:6574 [inline]
kmem_cache_free+0x16f/0x690 mm/slub.c:6684
blk_update_request+0x57e/0xe60 block/blk-mq.c:998
blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1160
nullb_complete_cmd drivers/block/null_blk/main.c:1402 [inline]
null_handle_cmd drivers/block/null_blk/main.c:1454 [inline]
null_queue_rq+0xbfe/0xe30 drivers/block/null_blk/main.c:1693
null_queue_rqs+0x123/0x270 drivers/block/null_blk/main.c:1707
__blk_mq_flush_list block/blk-mq.c:2837 [inline]
blk_mq_dispatch_queue_requests+0x417/0x800 block/blk-mq.c:2882
blk_mq_flush_plug_list+0x432/0x550 block/blk-mq.c:2970
__blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
blk_finish_plug+0x5e/0x90 block/blk-core.c:1252
blkdev_writepages+0x10e/0x170 block/fops.c:485
do_writepages+0x32e/0x550 mm/page-writeback.c:2604
filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
__filemap_fdatawrite_range mm/filemap.c:422 [inline]
file_write_and_wait_range+0x23e/0x340 mm/filemap.c:797
blkdev_fsync+0x74/0xd0 block/fops.c:616
generic_write_sync+0x1b3/0x290 include/linux/fs.h:3046
blkdev_write_iter+0x5fa/0x710 block/fops.c:803
iter_file_splice_write+0x975/0x10e0 fs/splice.c:738
do_splice_from fs/splice.c:938 [inline]
direct_splice_actor+0x101/0x160 fs/splice.c:1161
splice_direct_to_actor+0x5a8/0xcc0 fs/splice.c:1105
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0x181/0x270 fs/splice.c:1230
do_sendfile+0x4da/0x7e0 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f659d58eec9
RSP: 002b:00007f659e3c2038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f659d7e6180 RCX: 00007f659d58eec9
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000008
RBP: 00007f659d611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000200000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f659d7e6218 R14: 00007f659d7e6180 R15: 00007ffdd86d57e8
rcu: rcu_preempt kthread starved for 10577 jiffies! g156137 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:26464 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 33 31 0e 00 f3 0f 1e fa fb f4 c8 e6 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197de0 EFLAGS: 000002c6
RAX: 5b7d083a63995000 RBX: ffffffff81966c07 RCX: 5b7d083a63995000
RDX: 0000000000000001 RSI: ffffffff8d5161ee RDI: ffffffff8b9efde0
RBP: ffffc90000197f10 R08: ffff8880b8732fdb R09: 1ffff110170e65fb
R10: dffffc0000000000 R11: ffffed10170e65fc R12: ffffffff8f5c5670
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff11003954b58
FS: 0000000000000000(0000) GS:ffff888126269000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002740 CR3: 00000000311be000 CR4: 00000000003526f0
Call Trace:
arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
default_idle+0x13/0x20 arch/x86/kernel/process.c:767
default_idle_call+0x73/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:190 [inline]
do_idle+0x1e7/0x510 kernel/sched/idle.c:330
cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:428
start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:315
common_startup_64+0x13e/0x147