syzbot

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BUG: KASAN: slab-use-after-free in __list_del_entry_valid_or_report+0x92/0x190 lib/list_debug.c:62
Read of size 8 at addr ffff88807876d3f8 by task syz.2.1233/10498

CPU: 1 UID: 0 PID: 10498 Comm: syz.2.1233 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 __list_del_entry_valid_or_report+0x92/0x190 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+0xd9/0x8b0 fs/pnode.c:168
 umount_tree+0x577/0xd80 fs/namespace.c:1797
 put_mnt_ns+0x1d6/0x2f0 fs/namespace.c:6244
 nsproxy_free kernel/nsproxy.c:65 [inline]
 deactivate_nsproxy+0x41/0x140 kernel/nsproxy.c:79
 do_exit+0x68f/0x22f0 kernel/exit.c:970
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
 get_signal+0x1285/0x1340 kernel/signal.c:3034
 arch_do_signal_or_restart+0x9a/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x87/0x4e0 kernel/entry/common.c:75
 __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_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2c1/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcb3abc2005
Code: Unable to access opcode bytes at 0x7fcb3abc1fdb.
RSP: 002b:00007fcb3ba35f80 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007fcb3ade5fa0 RCX: 00007fcb3abc2005
RDX: 00007fcb3ba35fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fcb3ac13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 00007fcb3ade6038 R14: 00007fcb3ade5fa0 R15: 00007ffd1f3b4398
 </TASK>

Allocated by task 16256:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:5187 [inline]
 slab_alloc_node mm/slub.c:5500 [inline]
 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5507
 alloc_vfsmnt+0x23/0x420 fs/namespace.c:298
 clone_mnt+0x4b/0x9a0 fs/namespace.c:1257
 open_new_namespace fs/namespace.c:3110 [inline]
 vfs_open_tree+0x4e8/0xf50 fs/namespace.c:3220
 __do_sys_open_tree fs/namespace.c:3230 [inline]
 __se_sys_open_tree fs/namespace.c:3228 [inline]
 __x64_sys_open_tree+0x96/0x110 fs/namespace.c:3228
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 14261:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2768 [inline]
 slab_free mm/slub.c:6911 [inline]
 kmem_cache_free+0x195/0x630 mm/slub.c:7022
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core+0x7bd/0x1060 kernel/rcu/tree.c:2869
 handle_softirqs+0x22b/0x7c0 kernel/softirq.c:626
 __do_softirq kernel/softirq.c:660 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x60/0x150 kernel/softirq.c:727
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:743
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 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+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 __call_rcu_common kernel/rcu/tree.c:3131 [inline]
 call_rcu+0xee/0x890 kernel/rcu/tree.c:3251
 task_work_run+0x1d4/0x260 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:44 [inline]
 exit_to_user_mode_loop+0xef/0x4e0 kernel/entry/common.c:75
 __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_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2c1/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 task_work_add+0xb1/0x440 kernel/task_work.c:70
 mntput_no_expire_slowpath+0x710/0xbe0 fs/namespace.c:1390
 open_new_namespace fs/namespace.c:3175 [inline]
 vfs_open_tree+0xd76/0xf50 fs/namespace.c:3220
 __do_sys_open_tree fs/namespace.c:3230 [inline]
 __se_sys_open_tree fs/namespace.c:3228 [inline]
 __x64_sys_open_tree+0x96/0x110 fs/namespace.c:3228
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807876d340
 which belongs to the cache mnt_cache of size 352
The buggy address is located 184 bytes inside of
 freed 352-byte region [ffff88807876d340, ffff88807876d4a0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807876c380 pfn:0x7876c
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888021747801
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801bec5c80 0000000000000000 dead000000000001
raw: ffff88807876c380 000000088012000d 00000000f5000000 ffff888021747801
head: 00fff00000000040 ffff88801bec5c80 0000000000000000 dead000000000001
head: ffff88807876c380 000000088012000d 00000000f5000000 ffff888021747801
head: 00fff00000000001 ffffea0001e1db01 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 5827, tgid 5827 (syz-executor), ts 90887384803, free_ts 57447062917
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x23d/0x2a0 mm/page_alloc.c:1887
 prep_new_page mm/page_alloc.c:1895 [inline]
 get_page_from_freelist+0x23a5/0x2440 mm/page_alloc.c:3948
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5236
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3303 [inline]
 allocate_slab+0x87/0x670 mm/slub.c:3478
 new_slab mm/slub.c:3536 [inline]
 ___slab_alloc+0xdb6/0x17b0 mm/slub.c:4890
 __slab_alloc+0x65/0x100 mm/slub.c:5013
 __slab_alloc_node mm/slub.c:5089 [inline]
 slab_alloc_node mm/slub.c:5488 [inline]
 kmem_cache_alloc_noprof+0x40f/0x710 mm/slub.c:5507
 alloc_vfsmnt+0x23/0x420 fs/namespace.c:298
 clone_mnt+0x4b/0x9a0 fs/namespace.c:1257
 copy_tree+0x3d4/0x930 fs/namespace.c:2205
 copy_mnt_ns+0x11f/0x7c0 fs/namespace.c:4249
 create_new_namespaces+0xcf/0x6a0 kernel/nsproxy.c:98
 unshare_nsproxy_namespaces+0x11c/0x170 kernel/nsproxy.c:226
 ksys_unshare+0x4c8/0x8c0 kernel/fork.c:3168
 __do_sys_unshare kernel/fork.c:3239 [inline]
 __se_sys_unshare kernel/fork.c:3237 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3237
page last free pid 5586 tgid 5586 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1436 [inline]
 __free_frozen_pages+0xb99/0xd10 mm/page_alloc.c:2976
 discard_slab mm/slub.c:3580 [inline]
 __put_partials+0x146/0x170 mm/slub.c:4120
 __slab_free+0x294/0x320 mm/slub.c:6193
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:5187 [inline]
 slab_alloc_node mm/slub.c:5500 [inline]
 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5507
 mt_alloc_one lib/maple_tree.c:174 [inline]
 mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1110
 mas_preallocate+0x2e0/0x670 lib/maple_tree.c:5194
 vma_iter_prealloc mm/vma.h:505 [inline]
 commit_merge+0x203/0x700 mm/vma.c:751
 vma_expand+0x6dc/0xaf0 mm/vma.c:1200
 relocate_vma_down+0x2e8/0x500 mm/vma_exec.c:58
 setup_arg_pages+0x5cf/0xa90 fs/exec.c:690
 load_elf_binary+0xba4/0x2740 fs/binfmt_elf.c:1028
 search_binary_handler fs/exec.c:1664 [inline]
 exec_binprm fs/exec.c:1696 [inline]
 bprm_execve+0x92e/0x1400 fs/exec.c:1748
 do_execveat_common+0x50e/0x690 fs/exec.c:1846

Memory state around the buggy address:
 ffff88807876d280: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88807876d300: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff88807876d380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88807876d400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807876d480: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
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