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INFO: rcu detected stall in mremap

Status: upstream: reported on 2026/01/04 04:10
Reported-by: syzbot+fe55905227f40b0e1f08@syzkaller.appspotmail.com
First crash: 59d, last: 59d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in mremap 1 1 108d 108d 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 1504d 1504d 0/29 closed as invalid on 2022/02/08 10:10
upstream INFO: rcu detected stall in mremap (3) kernel 1 1 179d 179d 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 346d 346d 0/29 auto-obsoleted due to no activity on 2025/06/21 10:47
upstream INFO: rcu detected stall in sys_mremap mm 1 1 443d 443d 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: 	0-...!: (1 GPs behind) idle=d11c/1/0x4000000000000000 softirq=14976/14977 fqs=305
	(detected by 1, t=10505 jiffies, g=18717, q=745 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5366 Comm: syz.6.211 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:_raw_spin_lock_irqsave+0xdf/0xf0 kernel/locking/spinlock.c:162
Code: 36 e0 45 4b c7 04 27 00 00 00 00 65 48 8b 04 25 28 00 00 00 48 3b 44 24 48 75 10 4c 89 f0 48 8d 65 e0 5b 41 5c 41 5e 41 5f 5d <c3> e8 0b f1 f5 ff 66 2e 0f 1f 84 00 00 00 00 00 90 55 48 89 e5 41
RSP: 0018:ffffc90000007c90 EFLAGS: 00000046
RAX: 0000000000000802 RBX: ffff888055dbe340 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffc90000007b80
RBP: ffffc90000007e88 R08: 0000000000000004 R09: 0000000000000003
R10: fffff52000000f70 R11: 1ffff92000000f70 R12: ffff888055dbe340
R13: ffffffff96ca8b00 R14: 188f6ed29c000000 R15: dffffc0000000000
FS:  00007f63652a76c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c37df70 CR3: 000000007c678000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 debug_object_deactivate+0x63/0x340 lib/debugobjects.c:753
 debug_hrtimer_deactivate kernel/time/hrtimer.c:453 [inline]
 debug_deactivate+0x29/0x240 kernel/time/hrtimer.c:509
 __run_hrtimer kernel/time/hrtimer.c:1715 [inline]
 __hrtimer_run_queues+0x2df/0xd60 kernel/time/hrtimer.c:1811
 hrtimer_interrupt+0x3c5/0x9c0 kernel/time/hrtimer.c:1873
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:unwind_next_frame+0xbf/0x20b0 arch/x86/kernel/unwind_orc.c:436
Code: ac 24 98 00 00 00 4c 89 64 24 68 4c 89 7c 24 18 bf 01 00 00 00 e8 c1 5a 1f 00 4c 8d 7b 50 4c 89 f8 48 c1 e8 03 48 89 44 24 38 <42> 80 3c 30 00 74 08 4c 89 ff e8 a2 ab 98 00 4c 89 7c 24 10 4d 8b
RSP: 0018:ffffc900032bee10 EFLAGS: 00000a06
RAX: 1ffff92000657de7 RBX: ffffc900032beee8 RCX: ffffffff969cf100
RDX: dffffc0000000000 RSI: ffffffff81c20e63 RDI: ffffffff8138655f
RBP: ffffc900032bef30 R08: ffffc900032befb0 R09: 000000000000000c
R10: fffff52000657de9 R11: 1ffff92000657de7 R12: ffffffff81c20e63
R13: ffffc900032bfd28 R14: dffffc0000000000 R15: ffffc900032bef38
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free_bulk+0x348/0x460 mm/slub.c:3805
 mt_free_bulk lib/maple_tree.c:164 [inline]
 mas_destroy+0x2489/0x2c60 lib/maple_tree.c:5864
 mas_store_prealloc+0x31a/0x400 lib/maple_tree.c:5792
 do_mas_align_munmap+0xb43/0x1220 mm/mmap.c:2574
 do_mas_munmap+0x240/0x2b0 mm/mmap.c:2650
 do_munmap+0xd2/0x120 mm/mmap.c:2664
 move_vma+0x8b8/0xc70 mm/mremap.c:703
 mremap_to+0x529/0x5d0 mm/mremap.c:861
 __do_sys_mremap mm/mremap.c:972 [inline]
 __se_sys_mremap+0x603/0x10f0 mm/mremap.c:889
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f636438f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f63652a7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f63645e6180 RCX: 00007f636438f749
RDX: 0000000000002000 RSI: 0000000000002000 RDI: 0000200000ff9000
RBP: 00007f6364413f91 R08: 0000200000ffe000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f63645e6218 R14: 00007f63645e6180 R15: 00007ffcf6a19d88
 </TASK>
rcu: rcu_preempt kthread starved for 8980 jiffies! g18717 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:27904 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 5253 Comm: kworker/u4:17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: writeback wb_workfn (flush-8:0)
RIP: 0010:__sanitizer_cov_trace_pc+0x58/0x60 kernel/kcov.c:234
Code: f8 15 00 00 83 fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 48 8d 7e 01 8b 89 fc 15 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2 08 <c3> 0f 1f 80 00 00 00 00 48 8b 04 24 65 48 8b 15 04 8f 81 7e 65 8b
RSP: 0018:ffffc90004d0e518 EFLAGS: 00000293
RAX: ffffffff81760a02 RBX: dffffc0000000000 RCX: ffff888079eb5940
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90004d0e680 R08: dffffc0000000000 R09: fffff520009a1c95
R10: fffff520009a1c95 R11: 1ffff920009a1c94 R12: 1ffff110171c85b5
R13: ffff8880b8f3bb80 R14: 0000000000000000 R15: ffff8880b8e42da8
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5817517d60 CR3: 000000000c68e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 csd_lock_wait kernel/smp.c:424 [inline]
 smp_call_function_many_cond+0xe92/0x1270 kernel/smp.c:998
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1165
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:970 [inline]
 flush_tlb_mm_range+0x409/0x610 arch/x86/mm/tlb.c:1058
 flush_tlb_page arch/x86/include/asm/tlbflush.h:241 [inline]
 ptep_clear_flush+0x11c/0x160 mm/pgtable-generic.c:98
 page_vma_mkclean_one+0x400/0x680 mm/rmap.c:970
 page_mkclean_one+0x1d6/0x370 mm/rmap.c:1018
 rmap_walk_file+0x3e8/0x730 mm/rmap.c:2511
 rmap_walk mm/rmap.c:2529 [inline]
 folio_mkclean+0x1c4/0x330 mm/rmap.c:1050
 folio_clear_dirty_for_io+0x20a/0xc30 mm/page-writeback.c:2886
 mpage_submit_page+0x8a/0x210 fs/ext4/inode.c:2122
 mpage_process_page_bufs+0x6d8/0x8b0 fs/ext4/inode.c:2256
 mpage_prepare_extent_to_map+0xaf4/0x15d0 fs/ext4/inode.c:2681
 ext4_writepages+0xa22/0x2e50 fs/ext4/inode.c:2809
 do_writepages+0x3b7/0x610 mm/page-writeback.c:2491
 __writeback_single_inode+0x156/0x1160 fs/fs-writeback.c:1622
 writeback_sb_inodes+0xad8/0x17d0 fs/fs-writeback.c:1913
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:1984
 wb_writeback+0x47a/0xd00 fs/fs-writeback.c:2089
 wb_check_old_data_flush fs/fs-writeback.c:2189 [inline]
 wb_do_writeback fs/fs-writeback.c:2242 [inline]
 wb_workfn+0xb66/0xec0 fs/fs-writeback.c:2270
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/04 04:09 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in mremap
* Struck through repros no longer work on HEAD.