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 ffff88807630bb28 by task syz.3.11247/2093

CPU: 1 UID: 0 PID: 2093 Comm: syz.3.11247 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 need_secondary fs/pnode.c:263 [inline]
 propagate_mnt+0x1b3/0xd20 fs/pnode.c:336
 attach_recursive_mnt+0x5d7/0x2310 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+0x9c4/0xd30 fs/namespace.c:3836
 do_mount fs/namespace.c:4159 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4325
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f55cef9aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f55cfd85028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f55cf216090 RCX: 00007f55cef9aeb9
RDX: 0000200000000080 RSI: 0000200000000140 RDI: 0000000000000000
RBP: 00007f55cf008c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000189 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f55cf216128 R14: 00007f55cf216090 R15: 00007ffe92f278f8
 </TASK>

Allocated by task 27137:
 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:4456 [inline]
 slab_alloc_node mm/slub.c:4785 [inline]
 kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4792
 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+0x507/0x1040 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+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5827:
 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:2667 [inline]
 slab_free mm/slub.c:6079 [inline]
 kmem_cache_free+0x180/0x610 mm/slub.c:6205
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869
 handle_softirqs+0x22a/0x7c0 kernel/softirq.c:626
 do_softirq+0x76/0xd0 kernel/softirq.c:523
 __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 fpregs_unlock arch/x86/include/asm/fpu/api.h:77 [inline]
 copy_fpstate_to_sigframe+0x55c/0xd40 arch/x86/kernel/fpu/signal.c:220
 get_sigframe+0x5f7/0x820 arch/x86/kernel/signal.c:163
 x64_setup_rt_frame+0x160/0xcb0 arch/x86/kernel/signal_64.c:175
 setup_rt_frame arch/x86/kernel/signal.c:250 [inline]
 handle_signal arch/x86/kernel/signal.c:294 [inline]
 arch_do_signal_or_restart+0x424/0x830 arch/x86/kernel/signal.c:339
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 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_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

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+0x1d9/0x270 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+0xed/0x480 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_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 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+0xb6/0x440 kernel/task_work.c:70
 mntput_no_expire_slowpath+0x70c/0xbd0 fs/namespace.c:1379
 create_new_namespace fs/namespace.c:3162 [inline]
 open_new_namespace fs/namespace.c:3168 [inline]
 vfs_open_tree+0xe17/0x1040 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+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807630ba40
 which belongs to the cache mnt_cache of size 352
The buggy address is located 232 bytes inside of
 freed 352-byte region [ffff88807630ba40, ffff88807630bba0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807630bdc0 pfn:0x7630a
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888035f42a01
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff888140413640 ffff88801c2f77c8 ffffea0001f8a090
raw: ffff88807630bdc0 0000000800120010 00000000f5000000 ffff888035f42a01
head: 00fff00000000240 ffff888140413640 ffff88801c2f77c8 ffffea0001f8a090
head: ffff88807630bdc0 0000000800120010 00000000f5000000 ffff888035f42a01
head: 00fff00000000001 ffffea0001d8c281 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 5832, tgid 5832 (syz-executor), ts 76998856739, free_ts 26091087665
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1883
 prep_new_page mm/page_alloc.c:1891 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3956
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5244
 alloc_slab_page mm/slub.c:3235 [inline]
 allocate_slab+0x7b/0x660 mm/slub.c:3408
 new_slab mm/slub.c:3466 [inline]
 refill_objects+0x331/0x3c0 mm/slub.c:7084
 refill_sheaf mm/slub.c:2784 [inline]
 __pcs_replace_empty_main+0x2b9/0x620 mm/slub.c:4533
 alloc_from_pcs mm/slub.c:4636 [inline]
 slab_alloc_node mm/slub.c:4770 [inline]
 kmem_cache_alloc_noprof+0x37d/0x650 mm/slub.c:4792
 alloc_vfsmnt+0x23/0x420 fs/namespace.c:287
 clone_mnt+0x4b/0x9a0 fs/namespace.c:1246
 copy_tree+0x3d4/0x930 fs/namespace.c:2194
 copy_mnt_ns+0x24d/0x990 fs/namespace.c:4246
 create_new_namespaces+0xcf/0x6a0 kernel/nsproxy.c:98
 unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4f4/0x900 kernel/fork.c:3173
 __do_sys_unshare kernel/fork.c:3244 [inline]
 __se_sys_unshare kernel/fork.c:3242 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3242
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1432 [inline]
 __free_frozen_pages+0xc01/0xd80 mm/page_alloc.c:2972
 __free_pages mm/page_alloc.c:5363 [inline]
 free_contig_range+0xbb/0x170 mm/page_alloc.c:7367
 destroy_args+0x4e5/0x570 mm/debug_vm_pgtable.c:993
 debug_vm_pgtable+0x3f8/0x410 mm/debug_vm_pgtable.c:1368
 do_one_initcall+0x250/0x840 init/main.c:1382
 do_initcall_level+0x104/0x190 init/main.c:1444
 do_initcalls+0x59/0xa0 init/main.c:1460
 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
 kernel_init+0x1d/0x1d0 init/main.c:1582
 ret_from_fork+0x51b/0xa40 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:
 ffff88807630ba00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88807630ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807630bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88807630bb80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807630bc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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