syzbot

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BUG: KASAN: slab-use-after-free in __task_pid_nr_ns+0x1e4/0x490 kernel/pid.c:519
Read of size 8 at addr ffff88807f8058a8 by task syz.1.574/8108

CPU: 0 UID: 0 PID: 8108 Comm: syz.1.574 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 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
 __task_pid_nr_ns+0x1e4/0x490 kernel/pid.c:519
 perf_event_pid_type kernel/events/core.c:1432 [inline]
 perf_event_pid kernel/events/core.c:1441 [inline]
 perf_event_read_event kernel/events/core.c:8569 [inline]
 sync_child_event kernel/events/core.c:14087 [inline]
 perf_child_detach kernel/events/core.c:2340 [inline]
 __perf_remove_from_context+0x22e5/0x2a80 kernel/events/core.c:2511
 perf_remove_from_context+0x152/0x1d0 kernel/events/core.c:2560
 perf_event_release_kernel+0x2dd/0x510 kernel/events/core.c:5844
 perf_release+0x38/0x50 kernel/events/core.c:5877
 __fput+0x44c/0xa70 fs/file_table.c:468
 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+0xff/0x4f0 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+0x2e3/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9ee4f8f749
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:00007ffff9bb65a8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f9ee51e7da0 RCX: 00007f9ee4f8f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f9ee51e7da0 R08: 0000000000000000 R09: 00000011f9bb689f
R10: 00007f9ee51e7cb0 R11: 0000000000000246 R12: 000000000002c910
R13: 00007ffff9bb66a0 R14: ffffffffffffffff R15: 00007ffff9bb66c0
 </TASK>

Allocated by task 8109:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:342 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4948 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_noprof+0x367/0x6f0 mm/slub.c:5265
 copy_signal+0x50/0x650 kernel/fork.c:1656
 copy_process+0x15ff/0x3950 kernel/fork.c:2175
 kernel_clone+0x21e/0x820 kernel/fork.c:2608
 __do_sys_clone kernel/fork.c:2749 [inline]
 __se_sys_clone kernel/fork.c:2733 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2733
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 8109:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 __kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6663 [inline]
 kmem_cache_free+0x197/0x620 mm/slub.c:6774
 copy_process+0x26e6/0x3950 kernel/fork.c:2462
 kernel_clone+0x21e/0x820 kernel/fork.c:2608
 __do_sys_clone kernel/fork.c:2749 [inline]
 __se_sys_clone kernel/fork.c:2733 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2733
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807f805700
 which belongs to the cache signal_cache of size 1696
The buggy address is located 424 bytes inside of
 freed 1696-byte region [ffff88807f805700, ffff88807f805da0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7f800
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888021378c01
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b2fd780 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080110011 00000000f5000000 ffff888021378c01
head: 00fff00000000040 ffff88801b2fd780 dead000000000100 dead000000000122
head: 0000000000000000 0000000080110011 00000000f5000000 ffff888021378c01
head: 00fff00000000003 ffffea0001fe0001 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 12, tgid 12 (kworker/u8:0), ts 33341050073, free_ts 31533122865
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1845
 prep_new_page mm/page_alloc.c:1853 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3879
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xf2b/0x1960 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4774
 __slab_alloc_node mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:5246 [inline]
 kmem_cache_alloc_noprof+0x3f9/0x6f0 mm/slub.c:5265
 copy_signal+0x50/0x650 kernel/fork.c:1656
 copy_process+0x15ff/0x3950 kernel/fork.c:2175
 kernel_clone+0x21e/0x820 kernel/fork.c:2608
 user_mode_thread+0xdd/0x140 kernel/fork.c:2684
 call_usermodehelper_exec_sync kernel/umh.c:132 [inline]
 call_usermodehelper_exec_work+0x9c/0x230 kernel/umh.c:163
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
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:1394 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2901
 __free_pages mm/page_alloc.c:5302 [inline]
 free_contig_range+0x1bd/0x490 mm/page_alloc.c:7146
 destroy_args+0x69/0x660 mm/debug_vm_pgtable.c:958
 debug_vm_pgtable+0x39f/0x3b0 mm/debug_vm_pgtable.c:1345
 do_one_initcall+0x1fb/0x7f0 init/main.c:1283
 do_initcall_level+0x104/0x190 init/main.c:1345
 do_initcalls+0x59/0xa0 init/main.c:1361
 kernel_init_freeable+0x334/0x4b0 init/main.c:1593
 kernel_init+0x1d/0x1d0 init/main.c:1483
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff88807f805780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807f805800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807f805880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88807f805900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807f805980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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