Subject: Re: [syzbot] [kernel] WARNING: locking bug in try_to_wake_up

From: syzbot <[email-masked]>
Date: Mon, 30 Sep 2024 16:39:29 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    9852d85ec9d4 Linux 6.12-rc1
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16c0ddd0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1f009dd80b3799c2
dashboard link: https://syzkaller.appspot.com/bug?extid=8aaf2df2ef0164ffe1fb
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12017d07980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13ad839f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3a7fe74d3205/disk-9852d85e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0332f06aa08e/vmlinux-9852d85e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/58ddf291e00e/bzImage-9852d85e.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7b9a21b4b8c9/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/e0b9c39ab630/mount_2.gz
mounted in repro #3: https://storage.googleapis.com/syzbot-assets/6d11f8e19e12/mount_10.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: slab-use-after-free in __lock_acquire+0x77/0x2050 kernel/locking/lockdep.c:5065
Read of size 8 at addr ffff8880272a8a18 by task kworker/u8:3/52

CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 Not tainted 6.12.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: btrfs-fixup btrfs_work_helper
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 __lock_acquire+0x77/0x2050 kernel/locking/lockdep.c:5065
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
 class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]
 try_to_wake_up+0xb0/0x1480 kernel/sched/core.c:4154
 btrfs_writepage_fixup_worker+0xc16/0xdf0 fs/btrfs/inode.c:2842
 btrfs_work_helper+0x390/0xc50 fs/btrfs/async-thread.c:314
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 2:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:319 [inline]
 __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345
 kasan_slab_alloc include/linux/kasan.h:247 [inline]
 slab_post_alloc_hook mm/slub.c:4086 [inline]
 slab_alloc_node mm/slub.c:4135 [inline]
 kmem_cache_alloc_node_noprof+0x16b/0x320 mm/slub.c:4187
 alloc_task_struct_node kernel/fork.c:180 [inline]
 dup_task_struct+0x57/0x8c0 kernel/fork.c:1107
 copy_process+0x5d1/0x3d50 kernel/fork.c:2206
 kernel_clone+0x223/0x880 kernel/fork.c:2787
 kernel_thread+0x1bc/0x240 kernel/fork.c:2849
 create_kthread kernel/kthread.c:412 [inline]
 kthreadd+0x60d/0x810 kernel/kthread.c:765
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 61:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:2343 [inline]
 slab_free mm/slub.c:4580 [inline]
 kmem_cache_free+0x1a2/0x420 mm/slub.c:4682
 put_task_struct include/linux/sched/task.h:144 [inline]
 delayed_put_task_struct+0x125/0x300 kernel/exit.c:228
 rcu_do_batch kernel/rcu/tree.c:2567 [inline]
 rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823
 handle_softirqs+0x2c5/0x980 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1037 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1037
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Last potentially related work creation:
 kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
 __kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
 __call_rcu_common kernel/rcu/tree.c:3086 [inline]
 call_rcu+0x167/0xa70 kernel/rcu/tree.c:3190
 context_switch kernel/sched/core.c:5318 [inline]
 __schedule+0x184b/0x4ae0 kernel/sched/core.c:6675
 schedule_idle+0x56/0x90 kernel/sched/core.c:6793
 do_idle+0x56a/0x5d0 kernel/sched/idle.c:354
 cpu_startup_entry+0x42/0x60 kernel/sched/idle.c:424
 start_secondary+0x102/0x110 arch/x86/kernel/smpboot.c:314
 common_startup_64+0x13e/0x147

The buggy address belongs to the object at ffff8880272a8000
 which belongs to the cache task_struct of size 7424
The buggy address is located 2584 bytes inside of
 freed 7424-byte region [ffff8880272a8000, ffff8880272a9d00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x272a8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801bafa500 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080040004 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801bafa500 dead000000000122 0000000000000000
head: 0000000000000000 0000000080040004 00000001f5000000 0000000000000000
head: 00fff00000000003 ffffea00009caa01 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2, tgid 2 (kthreadd), ts 71247381401, free_ts 71214998153
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1545 [inline]
 get_page_from_freelist+0x3039/0x3180 mm/page_alloc.c:3457
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4733
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 alloc_slab_page+0x6a/0x120 mm/slub.c:2413
 allocate_slab+0x5a/0x2f0 mm/slub.c:2579
 new_slab mm/slub.c:2632 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3819
 __slab_alloc+0x58/0xa0 mm/slub.c:3909
 __slab_alloc_node mm/slub.c:3962 [inline]
 slab_alloc_node mm/slub.c:4123 [inline]
 kmem_cache_alloc_node_noprof+0x1fe/0x320 mm/slub.c:4187
 alloc_task_struct_node kernel/fork.c:180 [inline]
 dup_task_struct+0x57/0x8c0 kernel/fork.c:1107
 copy_process+0x5d1/0x3d50 kernel/fork.c:2206
 kernel_clone+0x223/0x880 kernel/fork.c:2787
 kernel_thread+0x1bc/0x240 kernel/fork.c:2849
 create_kthread kernel/kthread.c:412 [inline]
 kthreadd+0x60d/0x810 kernel/kthread.c:765
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page last free pid 5230 tgid 5230 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1108 [inline]
 free_unref_page+0xcd0/0xf00 mm/page_alloc.c:2638
 discard_slab mm/slub.c:2678 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:3146
 put_cpu_partial+0x17c/0x250 mm/slub.c:3221
 __slab_free+0x2ea/0x3d0 mm/slub.c:4450
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:247 [inline]
 slab_post_alloc_hook mm/slub.c:4086 [inline]
 slab_alloc_node mm/slub.c:4135 [inline]
 kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4142
 getname_flags+0xb7/0x540 fs/namei.c:139
 do_sys_openat2+0xd2/0x1d0 fs/open.c:1409
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0x247/0x2a0 fs/open.c:1441
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880272a8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880272a8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880272a8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8880272a8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880272a8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.