INFO: rcu detected stall in mremap (5)

Status: auto-obsoleted due to no activity on 2026/08/28 21:50
Subsystems: mm
Labels: prio:low
[Documentation on labels]
First crash: 93d, last: 93d
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ID Workflow Result Correct Bug Created Started Finished Revision
248981ae assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in mremap (5) 2026/06/02 21:29 2026/06/02 21:29 2026/06/02 22:37 62fe1528
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in mremap 1 1 288d 288d 0/3 auto-obsoleted due to no activity on 2026/02/24 13:38
upstream INFO: rcu detected stall in mremap kasan mm 1 1 1684d 1684d 0/29 closed as invalid on 2022/02/08 10:10
upstream INFO: rcu detected stall in mremap (4) mm 1 1 221d 221d 0/29 auto-obsoleted due to no activity on 2026/04/23 05:52
upstream INFO: rcu detected stall in mremap (3) kernel 1 1 359d 359d 0/29 auto-obsoleted due to no activity on 2025/11/05 16:37
upstream INFO: rcu detected stall in mremap (2) kasan mm 1 1 527d 527d 0/29 auto-obsoleted due to no activity on 2025/06/21 10:47
linux-6.1 INFO: rcu detected stall in mremap 1 1 240d 240d 0/3 auto-obsoleted due to no activity on 2026/04/14 04:10
upstream INFO: rcu detected stall in sys_mremap mm 1 1 623d 623d 0/29 auto-obsoleted due to no activity on 2025/03/16 11:40

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P12102/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=57221, q=1514 ncpus=2)
task:syz.2.1559      state:R  running task     stack:24104 pid:12102 tgid:12098 ppid:5636   task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x1821/0x5740 kernel/sched/core.c:7189
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7513
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x8b0 kernel/entry/common.c:164
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_lockdep_current_cpu_online+0xf3/0x120 kernel/rcu/tree.c:4052
Code: 4c 85 3b 75 1a 48 c7 c7 40 31 96 8e be 04 00 00 00 e8 01 fc 85 00 83 3d 2a 1e eb 0c 00 74 16 b0 01 65 ff 0d 0f 0d 8d 11 74 0f <5b> 41 5e 41 5f e9 de 2d 65 ff cc 31 c0 eb e8 e8 69 78 88 ff eb ea
RSP: 0018:ffffc90007b6eea0 EFLAGS: 00000286
RAX: 1ffffffff1d2c501 RBX: ffffffff8e9628b0 RCX: 0000000080000001
RDX: ffffc90004283000 RSI: ffffffff8c28b6c0 RDI: ffff8880b873bee8
RBP: dffffc0000000000 R08: ffffffff823c896a R09: ffffffff8e95cca0
R10: dffffc0000000000 R11: ffffed100a92cafe R12: 00000000000b44f4
R13: dffffc0000000000 R14: dffffc0000000000 R15: 0000000000000002
 rcu_read_lock_held_common kernel/rcu/update.c:113 [inline]
 rcu_read_lock_held+0x1e/0x50 kernel/rcu/update.c:349
 lookup_page_ext mm/page_ext.c:258 [inline]
 page_ext_lookup+0xe7/0x180 mm/page_ext.c:513
 page_ext_iter_begin include/linux/page_ext.h:133 [inline]
 __page_table_check_zero+0x135/0x3e0 mm/page_table_check.c:139
 page_table_check_free include/linux/page_table_check.h:46 [inline]
 __free_pages_prepare mm/page_alloc.c:1398 [inline]
 free_unref_folios+0xdae/0x14c0 mm/page_alloc.c:2999
 folios_put_refs+0x9ff/0xb40 mm/swap.c:1008
 free_pages_and_swap_cache+0x2b9/0x490 mm/swap_state.c:401
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:138 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:151 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:417 [inline]
 tlb_flush_mmu+0x6d3/0xa30 mm/mmu_gather.c:424
 tlb_finish_mmu+0xf9/0x230 mm/mmu_gather.c:549
 unmap_region+0x2a5/0x330 mm/vma.c:491
 vms_clear_ptes mm/vma.c:1303 [inline]
 vms_complete_munmap_vmas+0x493/0xc60 mm/vma.c:1345
 do_vmi_align_munmap+0x3b7/0x4b0 mm/vma.c:1604
 do_vmi_munmap+0x252/0x2d0 mm/vma.c:1652
 do_munmap+0xf9/0x170 mm/mmap.c:1067
 mremap_to+0x353/0x880 mm/mremap.c:1448
 do_mremap mm/mremap.c:1999 [inline]
 __do_sys_mremap mm/mremap.c:2055 [inline]
 __se_sys_mremap+0xe7a/0x11e0 mm/mremap.c:2023
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2ee939ce59
RSP: 002b:00007f2eea1bc028 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f2ee9615fa0 RCX: 00007f2ee939ce59
RDX: 0000000000800000 RSI: 0000000000002000 RDI: 0000200000ffb000
RBP: 00007f2ee9432d6f R08: 0000200000130000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2ee9616038 R14: 00007f2ee9615fa0 R15: 00007ffd368c7558
 </TASK>
rcu: rcu_preempt kthread starved for 10534 jiffies! g57221 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:26880 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x1821/0x5740 kernel/sched/core.c:7189
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7513
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x8b0 kernel/entry/common.c:164
 asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:704
RIP: 0010:constant_test_bit arch/x86/include/asm/bitops.h:202 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:232 [inline]
RIP: 0010:tif_test_bit include/linux/thread_info.h:199 [inline]
RIP: 0010:tif_need_resched include/linux/thread_info.h:215 [inline]
RIP: 0010:need_resched include/linux/sched.h:2286 [inline]
RIP: 0010:__schedule_loop kernel/sched/core.c:7270 [inline]
RIP: 0010:schedule+0x173/0x360 kernel/sched/core.c:7283
Code: 09 48 f7 03 10 00 00 00 74 2c bf 01 00 00 00 e8 b3 50 eb f5 31 ff e8 4c a7 ff ff bf 01 00 00 00 e8 42 52 eb f5 43 80 3c 2e 00 <74> d5 48 89 df e8 a3 95 88 f6 eb cb 4c 8d 73 2c 4d 89 f4 49 c1 ec
RSP: 0018:ffffc90000157a88 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffff88801daa0000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8c28b6c0 RDI: 00000000ffffffff
RBP: 1ffff11003b54003 R08: ffffffff903023f7 R09: 1ffffffff206047e
R10: dffffc0000000000 R11: fffffbfff206047f R12: ffff88801daa002c
R13: dffffc0000000000 R14: 1ffff11003b54000 R15: ffff88801daa1328
 schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x312/0x11d0 kernel/rcu/tree.c:2095
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297
 kthread+0x389/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 12137 Comm: syz.1.1564 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:246 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x10/0x90 kernel/kcov.c:321
Code: ff cc 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 04 24 65 48 8b 0d 78 64 72 11 <65> 8b 15 99 64 72 11 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75
RSP: 0018:ffffc900079bfd78 EFLAGS: 00000246
RAX: ffffffff816890f7 RBX: dffffc0000000000 RCX: ffff8880265f0000
RDX: ffffc90004bd1000 RSI: 00000000000000ca RDI: 00000000ffffffff
RBP: ffffc900079bfe90 R08: ffffffff903023f7 R09: 1ffffffff206047e
R10: dffffc0000000000 R11: fffffbfff206047f R12: 00000000000000ca
R13: 1ffff92000f37fb4 R14: ffff8880265f0000 R15: 00000000000000ca
FS:  00007f57fbc456c0(0000) GS:ffff88812529e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 000000002bead000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 handle_signal arch/x86/kernel/signal.c:264 [inline]
 arch_do_signal_or_restart+0x107/0x840 arch/x86/kernel/signal.c:339
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0xa9/0x680 kernel/entry/common.c:98
 __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:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f57fad9ce59
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:00007f57fbc450e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f57fb015fa8 RCX: 00007f57fad9ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f57fb015fa8
RBP: 00007f57fb015fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f57fb016038 R14: 00007ffd31ea10f0 R15: 00007ffd31ea11d8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/30 21:41 upstream f5e5d3509bff 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in mremap
* Struck through repros no longer work on HEAD.