Re: [syzbot] [mm?] INFO: rcu detected stall in sys_mprotect (8)

[syzbot <syzbot+6f7c31cf5ae4944ad6f0@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    303d91a15925 net: ipa: Drop unused qmi_elem_info arrays
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13bf72fd580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d30e1495ee3ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=6f7c31cf5ae4944ad6f0
compiler:       Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=108e8e55580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10b86bdd580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a7b8a5ad9a41/disk-303d91a1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74c1d7ed0168/vmlinux-303d91a1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/65d8cd3261b6/bzImage-303d91a1.xz

The issue was bisected to:

commit 5a781ccbd19e4664babcbe4b4ead7aa2b9283d22
Author: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Date:   Sat Sep 29 00:59:43 2018 +0000

    tc: Add support for configuring the taprio scheduler

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=124e5a18580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=114e5a18580000
console output: https://syzkaller.appspot.com/x/log.txt?x=164e5a18580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6f7c31cf5ae4944ad6f0@syzkaller.appspotmail.com
Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio scheduler")

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=d724/1/0x4000000000000000 softirq=20067/20067 fqs=59
rcu: 	(detected by 0, t=10503 jiffies, g=19585, q=576 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 6050 Comm: modprobe Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
RIP: 0010:__this_cpu_preempt_check+0x0/0x20 lib/smp_processor_id.c:63
Code: f5 48 8b 74 24 20 48 c7 c7 00 8d 8e 8c e8 e8 fc 24 f5 e8 b3 f8 2f f5 eb ae 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 48 89 fe 48 c7 c7 80 8c 8e 8c e9 0d ff ff ff cc cc cc
RSP: 0018:ffffc90000a08cb8 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000001000001
RDX: ffff8880247f0000 RSI: ffff8880226a42c0 RDI: ffffffff8e92d683
RBP: 00000000ffffffff R08: 0000000001000001 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000141190 R12: 0000000000000046
R13: ffff8880247f0000 R14: ffff8880226a42c0 R15: 0000000000000001
FS:  00007f2cd712ac80(0000) GS:ffff88812371f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2cd7492000 CR3: 0000000078d22000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lockdep_recursion_finish kernel/locking/lockdep.c:470 [inline]
 lock_is_held_type+0xdf/0x150 kernel/locking/lockdep.c:6017
 lock_is_held include/linux/lockdep.h:249 [inline]
 advance_sched+0x1d9/0xc80 net/sched/sch_taprio.c:944
 __run_hrtimer kernel/time/hrtimer.c:2075 [inline]
 __hrtimer_run_queues+0x3bc/0xa10 kernel/time/hrtimer.c:2132
 hrtimer_interrupt+0x4cd/0xaa0 kernel/time/hrtimer.c:2251
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:check_kcov_mode kernel/kcov.c:179 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x18/0x80 kernel/kcov.c:223
Code: cc cc 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 28 fa f6 12 65 48 8b 15 28 fa f6 12 <f7> c2 00 01 00 ff 74 29 89 d6 81 e6 00 01 00 0f 81 fe 00 01 00 00
RSP: 0018:ffffc9000376f4b8 EFLAGS: 00000202
RAX: ffffffff8bfb23dd RBX: 0000000000000001 RCX: ffff8880247f0000
RDX: 8000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffff888077514e00 R08: ffff8880247f0000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000000 R12: ffff88807bdef180
R13: ffff88802ad9bc80 R14: 0000000000000001 R15: dffffc0000000000
 mt_slot lib/maple_tree.c:676 [inline]
 mas_next_slot+0x9dd/0xd70 lib/maple_tree.c:4228
 mas_find+0x6d6/0xcb0 lib/maple_tree.c:5451
 vma_next include/linux/mm.h:1816 [inline]
 validate_mm+0xff/0x4c0 mm/vma.c:680
 __split_vma+0x94a/0xa90 mm/vma.c:597
 split_vma mm/vma.c:626 [inline]
 vma_modify+0xa3f/0x1c50 mm/vma.c:1772
 vma_modify_flags+0x2a4/0x3c0 mm/vma.c:1792
 mprotect_fixup+0x539/0xda0 mm/mprotect.c:823
 do_mprotect_pkey+0x8e7/0xd40 mm/mprotect.c:1001
 __do_sys_mprotect mm/mprotect.c:1022 [inline]
 __se_sys_mprotect mm/mprotect.c:1019 [inline]
 __x64_sys_mprotect+0x80/0x90 mm/mprotect.c:1019
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2cd74c12c7
Code: 89 3d fd 3f 01 00 eb 90 0f 1f 00 f7 d8 89 05 f0 3f 01 00 48 c7 c0 ff ff ff ff eb 91 0f 1f 80 00 00 00 00 b8 0a 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d c9 3f 01 00 f7 d8 89 01 48 83
RSP: 002b:00007fff152bcf58 EFLAGS: 00000206 ORIG_RAX: 000000000000000a
RAX: ffffffffffffffda RBX: 00007f2cd74d4da0 RCX: 00007f2cd74c12c7
RDX: 0000000000000001 RSI: 0000000000002000 RDI: 00007f2cd74d2000
RBP: 00007fff152bd220 R08: 000000003de00ec7 R09: 0000000000000000
R10: 00007f2cd7205c58 R11: 0000000000000206 R12: fffffffffffffff8
R13: 000000418bb1d7ff R14: 0000000000000000 R15: 00007f2cd74d5310
 </TASK>
rcu: rcu_preempt kthread starved for 10208 jiffies! g19585 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->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:27496 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5583 [inline]
 __schedule+0x17dd/0x5830 kernel/sched/core.c:7382
 __schedule_loop kernel/sched/core.c:7459 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7474
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x1230 kernel/rcu/tree.c:2122
 rcu_gp_kthread+0x9c/0x340 kernel/rcu/tree.c:2330
 kthread+0x38b/0x480 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:
CPU: 0 UID: 0 PID: 5670 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
RIP: 0010:csd_lock_wait kernel/smp.c:389 [inline]
RIP: 0010:csd_lock kernel/smp.c:422 [inline]
RIP: 0010:smp_call_function_many_cond+0x61e/0x1500 kernel/smp.c:970
Code: b6 04 04 84 c0 0f 85 d5 03 00 00 44 8b 3b 44 89 fe 83 e6 01 31 ff e8 21 7a 0c 00 41 83 e7 01 75 07 e8 06 75 0c 00 eb 3f f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 0f f7 03 01
RSP: 0000:ffffc9000436f720 EFLAGS: 00000293
RAX: ffffffff81bca0ee RBX: ffff8880b8341d88 RCX: ffff888033b79f40
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000436f870 R08: ffff888033b7b4df R09: 1ffff1100676f69b
R10: dffffc0000000000 R11: ffffffff817a65a0 R12: 1ffff110170683b1
R13: 0000000000000001 R14: ffff8880b8341d80 R15: 0000000000000001
FS:  00007fe06f357880(0000) GS:ffff88812361f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557f8f49d568 CR3: 00000000692c0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
 flush_tlb_mm_range+0x910/0x10b0 arch/x86/mm/tlb.c:1435
 flush_tlb_page arch/x86/include/asm/tlbflush.h:352 [inline]
 ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:116
 wp_page_copy mm/memory.c:4136 [inline]
 do_wp_page+0x3c3a/0x4b60 mm/memory.c:4535
 handle_pte_fault mm/memory.c:6651 [inline]
 __handle_mm_fault mm/memory.c:6776 [inline]
 handle_mm_fault+0x15d7/0x3750 mm/memory.c:6943
 do_user_addr_fault+0xb35/0x1480 arch/x86/mm/fault.c:1343
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7fe06f3f1b69
Code: 10 48 81 f9 ff 03 00 00 76 28 48 8b 57 20 48 85 d2 74 1f 48 3b 7a 28 75 76 48 8b 4f 28 48 3b 79 20 75 6c 48 83 78 20 00 74 17 <48> 89 4a 28 48 89 51 20 48 83 c4 08 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffe7da68c0 EFLAGS: 00010206
RAX: 00007fe06f52e1d0 RBX: 0000557f8f49d540 RCX: 0000557f8f49d540
RDX: 0000557f8f49d540 RSI: 00007fe06f52e1d0 RDI: 0000557f8f49d540
RBP: 00007fe06f52dac0 R08: 0000000000002760 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000000049c0
R13: 0000557f8f4a1f00 R14: 0000000000000160 R15: 00007fe06f52dac0
 </TASK>


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