syzbot

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BUG: KASAN: slab-use-after-free in __list_del_entry_valid_or_report+0x1b1/0x1d0 lib/list_debug.c:62
Read of size 8 at addr ffff88807d533af8 by task syz.6.6371/24241

CPU: 1 UID: 0 PID: 24241 Comm: syz.6.6371 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x156/0x4c9 mm/kasan/report.c:482
 kasan_report+0xdf/0x1e0 mm/kasan/report.c:595
 __list_del_entry_valid_or_report+0x1b1/0x1d0 lib/list_debug.c:62
 __list_del_entry_valid include/linux/list.h:132 [inline]
 __list_del_entry include/linux/list.h:223 [inline]
 list_del_init include/linux/list.h:295 [inline]
 trace_transfers fs/pnode.c:132 [inline]
 bulk_make_private+0xd8/0x720 fs/pnode.c:168
 umount_tree+0x3fb/0xec0 fs/namespace.c:1786
 put_mnt_ns+0x267/0x300 fs/namespace.c:6230
 nsproxy_free kernel/nsproxy.c:65 [inline]
 deactivate_nsproxy kernel/nsproxy.c:79 [inline]
 put_nsproxy include/linux/nsproxy.h:110 [inline]
 put_nsproxy include/linux/nsproxy.h:107 [inline]
 switch_task_namespaces+0x133/0x2c0 kernel/nsproxy.c:252
 do_exit+0x824/0x2aa0 kernel/exit.c:970
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1112
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x67c/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb59019c629
Code: Unable to access opcode bytes at 0x7fb59019c5ff.
RSP: 002b:00007fb58e3f6028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: 000000000003ffff RBX: 00007fb590416090 RCX: 00007fb59019c629
RDX: 00000000080002c1 RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007fb590232b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb590416128 R14: 00007fb590416090 R15: 00007fffb7232398
 </TASK>

Allocated by task 23694:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4501 [inline]
 slab_alloc_node mm/slub.c:4830 [inline]
 kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4837
 alloc_vfsmnt+0x23/0x6a0 fs/namespace.c:287
 clone_mnt+0x4b/0x930 fs/namespace.c:1246
 create_new_namespace fs/namespace.c:3098 [inline]
 open_new_namespace fs/namespace.c:3168 [inline]
 vfs_open_tree+0xb02/0x1500 fs/namespace.c:3217
 __do_sys_open_tree fs/namespace.c:3227 [inline]
 __se_sys_open_tree fs/namespace.c:3225 [inline]
 __x64_sys_open_tree+0xa3/0x150 fs/namespace.c:3225
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 0:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2687 [inline]
 slab_free mm/slub.c:6124 [inline]
 kmem_cache_free+0x124/0x6a0 mm/slub.c:6254
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2869
 handle_softirqs+0x1eb/0x9e0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xef/0x150 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697

Last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 __call_rcu_common.constprop.0+0xa5/0x9b0 kernel/rcu/tree.c:3131
 task_work_run+0x150/0x240 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x100/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x67c/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Second to last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 task_work_add+0x28b/0x3b0 kernel/task_work.c:70
 mntput_no_expire_slowpath+0x3da/0xb00 fs/namespace.c:1379
 mntput_no_expire+0x1fd/0x220 fs/namespace.c:1406
 mntput+0x6b/0xa0 fs/namespace.c:1416
 create_new_namespace fs/namespace.c:3082 [inline]
 open_new_namespace fs/namespace.c:3168 [inline]
 vfs_open_tree+0x1235/0x1500 fs/namespace.c:3217
 __do_sys_open_tree fs/namespace.c:3227 [inline]
 __se_sys_open_tree fs/namespace.c:3225 [inline]
 __x64_sys_open_tree+0xa3/0x150 fs/namespace.c:3225
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807d533a40
 which belongs to the cache mnt_cache of size 352
The buggy address is located 184 bytes inside of
 freed 352-byte region [ffff88807d533a40, ffff88807d533ba0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807d532fc0 pfn:0x7d532
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88807d532171
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff888140416140 ffffea0000961010 ffffea0001e52990
raw: ffff88807d532fc0 000001c000120005 00000000f5000000 ffff88807d532171
head: 00fff00000000240 ffff888140416140 ffffea0000961010 ffffea0001e52990
head: ffff88807d532fc0 000001c000120005 00000000f5000000 ffff88807d532171
head: 00fff00000000001 ffffea0001f54c81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5956, tgid 5955 (syz.4.15), ts 66014645699, free_ts 65711879813
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1889
 prep_new_page mm/page_alloc.c:1897 [inline]
 get_page_from_freelist+0x111d/0x3140 mm/page_alloc.c:3962
 __alloc_frozen_pages_noprof+0x27c/0x2ba0 mm/page_alloc.c:5250
 alloc_slab_page mm/slub.c:3255 [inline]
 allocate_slab mm/slub.c:3444 [inline]
 new_slab+0xa6/0x6d0 mm/slub.c:3502
 refill_objects+0x26b/0x400 mm/slub.c:7134
 refill_sheaf mm/slub.c:2804 [inline]
 alloc_full_sheaf mm/slub.c:2825 [inline]
 __pcs_replace_empty_main+0x19f/0x600 mm/slub.c:4588
 alloc_from_pcs mm/slub.c:4681 [inline]
 slab_alloc_node mm/slub.c:4815 [inline]
 kmem_cache_alloc_noprof+0x480/0x6e0 mm/slub.c:4837
 alloc_vfsmnt+0x23/0x6a0 fs/namespace.c:287
 clone_mnt+0x4b/0x930 fs/namespace.c:1246
 copy_tree+0x329/0xbf0 fs/namespace.c:2194
 copy_mnt_ns+0x2bd/0xc30 fs/namespace.c:4246
 create_new_namespaces+0xd3/0xac0 kernel/nsproxy.c:98
 unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x455/0xab0 kernel/fork.c:3174
 __do_sys_unshare kernel/fork.c:3245 [inline]
 __se_sys_unshare kernel/fork.c:3243 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3243
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 1219 tgid 1219 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0x7e1/0x10d0 mm/page_alloc.c:2978
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xe0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4501 [inline]
 slab_alloc_node mm/slub.c:4830 [inline]
 __kmalloc_cache_noprof+0x243/0x6f0 mm/slub.c:5334
 kmalloc_noprof include/linux/slab.h:962 [inline]
 kzalloc_noprof include/linux/slab.h:1204 [inline]
 nsim_fib6_rt_create drivers/net/netdevsim/fib.c:547 [inline]
 nsim_fib6_rt_insert drivers/net/netdevsim/fib.c:752 [inline]
 nsim_fib6_event drivers/net/netdevsim/fib.c:856 [inline]
 nsim_fib_event drivers/net/netdevsim/fib.c:889 [inline]
 nsim_fib_event_work+0x157b/0x63b0 drivers/net/netdevsim/fib.c:1493
 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
 process_scheduled_works kernel/workqueue.c:3358 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
 kthread+0x370/0x450 kernel/kthread.c:467
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88807d533980: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88807d533a00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff88807d533a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88807d533b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807d533b80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
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