================================================================== BUG: KASAN: use-after-free in atomic_fetch_add include/asm-generic/atomic-instrumented.h:111 [inline] BUG: KASAN: use-after-free in refcount_add include/linux/refcount.h:188 [inline] BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:228 [inline] BUG: KASAN: use-after-free in get_task_struct include/linux/sched/task.h:112 [inline] BUG: KASAN: use-after-free in kthread_stop+0x37/0x4a0 kernel/kthread.c:612 Write of size 4 at addr ffff8881ee7acee0 by task syz-executor.3/373 CPU: 0 PID: 373 Comm: syz-executor.3 Not tainted 5.4.274-syzkaller-00002-g6f97bd951d82 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1d8/0x241 lib/dump_stack.c:118 print_address_description+0x8c/0x600 mm/kasan/report.c:384 __kasan_report+0xf3/0x120 mm/kasan/report.c:516 kasan_report+0x30/0x60 mm/kasan/common.c:653 check_memory_region_inline mm/kasan/generic.c:141 [inline] check_memory_region+0x272/0x280 mm/kasan/generic.c:191 atomic_fetch_add include/asm-generic/atomic-instrumented.h:111 [inline] refcount_add include/linux/refcount.h:188 [inline] refcount_inc include/linux/refcount.h:228 [inline] get_task_struct include/linux/sched/task.h:112 [inline] kthread_stop+0x37/0x4a0 kernel/kthread.c:612 ext4_put_super+0x790/0xbb0 fs/ext4/super.c:1055 generic_shutdown_super+0x120/0x2a0 fs/super.c:464 kill_block_super+0x7a/0xe0 fs/super.c:1453 deactivate_locked_super+0xa8/0x110 fs/super.c:335 deactivate_super+0x1e2/0x2a0 fs/super.c:366 cleanup_mnt+0x44e/0x500 fs/namespace.c:1102 task_work_run+0x140/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x190/0x1a0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 RIP: 0033:0x7f3a96c8f3d7 Code: b0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 b0 ff ff ff f7 d8 64 89 02 b8 RSP: 002b:00007ffe30551c58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f3a96c8f3d7 RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe30551d10 RBP: 00007ffe30551d10 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffe30552dc0 R13: 00007f3a96cea6c6 R14: 0000000000006a39 R15: 0000000000000005 Allocated by task 2: save_stack mm/kasan/common.c:70 [inline] set_track mm/kasan/common.c:78 [inline] __kasan_kmalloc+0x171/0x210 mm/kasan/common.c:529 slab_post_alloc_hook mm/slab.h:584 [inline] slab_alloc_node mm/slub.c:2829 [inline] slab_alloc mm/slub.c:2837 [inline] kmem_cache_alloc+0xd9/0x250 mm/slub.c:2842 kmem_cache_alloc_node include/linux/slab.h:427 [inline] alloc_task_struct_node kernel/fork.c:171 [inline] dup_task_struct+0x4f/0x600 kernel/fork.c:882 copy_process+0x56d/0x3230 kernel/fork.c:1889 _do_fork+0x197/0x900 kernel/fork.c:2399 kernel_thread+0x16a/0x1d0 kernel/fork.c:2489 create_kthread kernel/kthread.c:311 [inline] kthreadd+0x3b1/0x4f0 kernel/kthread.c:654 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354 Freed by task 485: save_stack mm/kasan/common.c:70 [inline] set_track mm/kasan/common.c:78 [inline] kasan_set_free_info mm/kasan/common.c:345 [inline] __kasan_slab_free+0x1b5/0x270 mm/kasan/common.c:487 slab_free_hook mm/slub.c:1455 [inline] slab_free_freelist_hook mm/slub.c:1494 [inline] slab_free mm/slub.c:3080 [inline] kmem_cache_free+0x10b/0x2c0 mm/slub.c:3096 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x492/0xa00 kernel/rcu/tree.c:2167 rcu_core+0x4c8/0xcb0 kernel/rcu/tree.c:2387 __do_softirq+0x23b/0x6b7 kernel/softirq.c:292 The buggy address belongs to the object at ffff8881ee7acec0 which belongs to the cache task_struct of size 3904 The buggy address is located 32 bytes inside of 3904-byte region [ffff8881ee7acec0, ffff8881ee7ade00) The buggy address belongs to the page: page:ffffea0007b9ea00 refcount:1 mapcount:0 mapping:ffff8881f5cf8780 index:0x0 compound_mapcount: 0 flags: 0x8000000000010200(slab|head) raw: 8000000000010200 ffffea0007c36000 0000000300000003 ffff8881f5cf8780 raw: 0000000000000000 0000000080080008 00000001ffffffff 0000000000000000 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) set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook mm/page_alloc.c:2165 [inline] prep_new_page+0x18f/0x370 mm/page_alloc.c:2171 get_page_from_freelist+0x2d13/0x2d90 mm/page_alloc.c:3794 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4893 alloc_slab_page+0x39/0x3c0 mm/slub.c:343 allocate_slab mm/slub.c:1683 [inline] new_slab+0x97/0x440 mm/slub.c:1749 new_slab_objects mm/slub.c:2505 [inline] ___slab_alloc+0x2fe/0x490 mm/slub.c:2667 __slab_alloc+0x62/0xa0 mm/slub.c:2707 slab_alloc_node mm/slub.c:2792 [inline] slab_alloc mm/slub.c:2837 [inline] kmem_cache_alloc+0x109/0x250 mm/slub.c:2842 kmem_cache_alloc_node include/linux/slab.h:427 [inline] alloc_task_struct_node kernel/fork.c:171 [inline] dup_task_struct+0x4f/0x600 kernel/fork.c:882 copy_process+0x56d/0x3230 kernel/fork.c:1889 _do_fork+0x197/0x900 kernel/fork.c:2399 kernel_thread+0x16a/0x1d0 kernel/fork.c:2489 create_kthread kernel/kthread.c:311 [inline] kthreadd+0x3b1/0x4f0 kernel/kthread.c:654 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1176 [inline] __free_pages_ok+0x847/0x950 mm/page_alloc.c:1438 free_the_page mm/page_alloc.c:4955 [inline] __free_pages+0x91/0x140 mm/page_alloc.c:4961 free_thread_stack kernel/fork.c:299 [inline] release_task_stack kernel/fork.c:439 [inline] put_task_stack+0x212/0x260 kernel/fork.c:450 finish_task_switch+0x24a/0x590 kernel/sched/core.c:3479 context_switch kernel/sched/core.c:3611 [inline] __schedule+0xb0d/0x1320 kernel/sched/core.c:4307 schedule_idle+0x50/0x80 kernel/sched/core.c:4403 do_idle+0x609/0x660 kernel/sched/idle.c:288 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:356 start_secondary+0x3a5/0x460 arch/x86/kernel/smpboot.c:277 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 Memory state around the buggy address: ffff8881ee7acd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8881ee7ace00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc >ffff8881ee7ace80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8881ee7acf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881ee7acf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 373 at lib/refcount.c:25 refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Modules linked in: CPU: 1 PID: 373 Comm: syz-executor.3 Tainted: G B 5.4.274-syzkaller-00002-g6f97bd951d82 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024 RIP: 0010:refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Code: 04 01 48 c7 c7 a0 0b fa 84 e8 6a ef 0d ff 0f 0b eb a9 e8 31 3b 37 ff c6 05 c4 97 1c 04 01 48 c7 c7 20 0c fa 84 e8 4e ef 0d ff <0f> 0b eb 8d e8 15 3b 37 ff c6 05 a9 97 1c 04 01 48 c7 c7 80 0c fa RSP: 0018:ffff8881d757fc30 EFLAGS: 00010246 RAX: bb3c812bb5526100 RBX: 0000000000000002 RCX: ffff8881d8b58000 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: 0000000000000002 R08: ffffffff814d5cd2 R09: ffffed103ede5262