syzbot

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BUG: KASAN: slab-use-after-free in need_secondary fs/pnode.c:263 [inline]
BUG: KASAN: slab-use-after-free in propagate_mnt+0x1b3/0xd20 fs/pnode.c:336
Read of size 8 at addr ffff88805acf1268 by task syz.8.10043/1570

CPU: 0 UID: 0 PID: 1570 Comm: syz.8.10043 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
 need_secondary fs/pnode.c:263 [inline]
 propagate_mnt+0x1b3/0xd20 fs/pnode.c:336
 attach_recursive_mnt+0x48a/0x2290 fs/namespace.c:2588
 graft_tree fs/namespace.c:2813 [inline]
 do_add_mount fs/namespace.c:3747 [inline]
 do_new_mount_fc fs/namespace.c:3779 [inline]
 do_new_mount+0x995/0xcf0 fs/namespace.c:3836
 do_mount fs/namespace.c:4159 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4325
 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
RIP: 0033:0x7fe9f1d8f749
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:00007fe9f2bf1038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe9f1fe5fa0 RCX: 00007fe9f1d8f749
RDX: 0000200000000180 RSI: 0000200000000080 RDI: 0000000000000000
RBP: 00007fe9f1e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000003200890 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe9f1fe6038 R14: 00007fe9f1fe5fa0 R15: 00007ffcc67ed5e8
 </TASK>

Allocated by task 313:
 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:4411 [inline]
 slab_alloc_node mm/slub.c:4740 [inline]
 kmem_cache_alloc_noprof+0x2bd/0x660 mm/slub.c:4747
 alloc_vfsmnt+0x23/0x420 fs/namespace.c:287
 clone_mnt+0x4b/0x9a0 fs/namespace.c:1246
 create_new_namespace fs/namespace.c:3098 [inline]
 open_new_namespace fs/namespace.c:3168 [inline]
 vfs_open_tree+0x4e9/0x1010 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+0x96/0x110 fs/namespace.c:3225
 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 15:
 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:2627 [inline]
 slab_free mm/slub.c:6013 [inline]
 kmem_cache_free+0x192/0x5d0 mm/slub.c:6126
 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
 run_ksoftirqd+0x36/0x60 kernel/softirq.c:1067
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x389/0x480 kernel/kthread.c:467
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

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:1379
 create_new_namespace fs/namespace.c:3162 [inline]
 open_new_namespace fs/namespace.c:3168 [inline]
 vfs_open_tree+0xdf9/0x1010 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+0x96/0x110 fs/namespace.c:3225
 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 ffff88805acf1180
 which belongs to the cache mnt_cache of size 352
The buggy address is located 232 bytes inside of
 freed 352-byte region [ffff88805acf1180, ffff88805acf12e0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88805acf1dc0 pfn:0x5acf0
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88805acf0171
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff888140410640 ffffea00008bc210 ffffea0000d19890
raw: ffff88805acf1dc0 000001c000120001 00000000f5000000 ffff88805acf0171
head: 00fff00000000240 ffff888140410640 ffffea00008bc210 ffffea0000d19890
head: ffff88805acf1dc0 000001c000120001 00000000f5000000 ffff88805acf0171
head: 00fff00000000001 ffffea00016b3c01 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 11385, tgid 11384 (syz.3.1212), ts 331799538163, free_ts 331780645091
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x23d/0x2a0 mm/page_alloc.c:1883
 prep_new_page mm/page_alloc.c:1891 [inline]
 get_page_from_freelist+0x24e0/0x2580 mm/page_alloc.c:3956
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5244
 alloc_slab_page mm/slub.c:3195 [inline]
 allocate_slab+0x7b/0x670 mm/slub.c:3368
 new_slab mm/slub.c:3426 [inline]
 refill_objects+0x343/0x3e0 mm/slub.c:7002
 refill_sheaf mm/slub.c:2744 [inline]
 __pcs_replace_empty_main+0x2bb/0x620 mm/slub.c:4488
 alloc_from_pcs mm/slub.c:4591 [inline]
 slab_alloc_node mm/slub.c:4725 [inline]
 kmem_cache_alloc_noprof+0x37c/0x660 mm/slub.c:4747
 alloc_vfsmnt+0x23/0x420 fs/namespace.c:287
 vfs_create_mount+0x69/0x320 fs/namespace.c:1178
 __do_sys_fsmount fs/namespace.c:4460 [inline]
 __se_sys_fsmount+0x506/0xad0 fs/namespace.c:4393
 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
page last free pid 11383 tgid 11383 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1432 [inline]
 __free_frozen_pages+0xbd1/0xd40 mm/page_alloc.c:2972
 mm_free_pgd kernel/fork.c:584 [inline]
 __mmdrop+0xb6/0x750 kernel/fork.c:726
 exec_mmap+0x3b5/0x440 fs/exec.c:893
 begin_new_exec+0x1353/0x2440 fs/exec.c:1148
 load_elf_binary+0x998/0x2740 fs/binfmt_elf.c:1010
 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
 __do_sys_execve fs/exec.c:1930 [inline]
 __se_sys_execve fs/exec.c:1924 [inline]
 __x64_sys_execve+0x97/0xc0 fs/exec.c:1924
 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

Memory state around the buggy address:
 ffff88805acf1100: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805acf1180: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805acf1200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff88805acf1280: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88805acf1300: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
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