================================================================== 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 ffff8881e41a5ea0 by task syz-executor/552 CPU: 0 PID: 552 Comm: syz-executor Not tainted 5.4.290-syzkaller-00017-g6b07fcd94a6a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 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+0x120/0x300 fs/super.c:464 kill_block_super+0x7a/0xe0 fs/super.c:1455 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 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0xcaf/0x2bc0 kernel/exit.c:861 do_group_exit+0x138/0x300 kernel/exit.c:984 __do_sys_exit_group kernel/exit.c:995 [inline] __se_sys_exit_group kernel/exit.c:993 [inline] __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:993 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 RIP: 0033:0x7ff262431169 Code: Bad RIP value. RSP: 002b:00007ffdbb392e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 00007ff2624b20b1 RCX: 00007ff262431169 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001 RBP: 0000000000000075 R08: 00007ffdbb390c05 R09: 00007ffdbb394120 R10: 000000000000000b R11: 0000000000000246 R12: 00007ffdbb394120 R13: 00007ff2624b208c R14: 000055558a6784a8 R15: 00007ffdbb3951f0 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 17: 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 ffff8881e41a5e80 which belongs to the cache task_struct of size 3904 The buggy address is located 32 bytes inside of 3904-byte region [ffff8881e41a5e80, ffff8881e41a6dc0) The buggy address belongs to the page: page:ffffea0007906800 refcount:1 mapcount:0 mapping:ffff8881f5cf1400 index:0x0 compound_mapcount: 0 flags: 0x8000000000010200(slab|head) raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5cf1400 raw: 0000000000000000 0000000000080008 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL) 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_pcp_prepare mm/page_alloc.c:1233 [inline] free_unref_page_prepare+0x297/0x380 mm/page_alloc.c:3085 free_unref_page mm/page_alloc.c:3134 [inline] free_the_page mm/page_alloc.c:4953 [inline] __free_pages+0xaf/0x140 mm/page_alloc.c:4961 __vunmap+0x75b/0x890 mm/vmalloc.c:2260 kcov_mmap+0x8c/0x120 kernel/kcov.c:474 call_mmap include/linux/fs.h:1996 [inline] mmap_region+0x110d/0x16f0 mm/mmap.c:1812 do_mmap+0x822/0xd30 mm/mmap.c:1581 do_mmap_pgoff include/linux/mm.h:2480 [inline] vm_mmap_pgoff+0x1b5/0x260 mm/util.c:528 ksys_mmap_pgoff+0x168/0x1e0 mm/mmap.c:1631 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 Memory state around the buggy address: ffff8881e41a5d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8881e41a5e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8881e41a5e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881e41a5f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881e41a5f80: 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: 0 PID: 552 at lib/refcount.c:25 refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 552 Comm: syz-executor Tainted: G B 5.4.290-syzkaller-00017-g6b07fcd94a6a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 RIP: 0010:refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Code: 04 01 48 c7 c7 e0 1f fa 84 e8 ba 8b 0d ff 0f 0b eb a9 e8 c1 e9 36 ff c6 05 96 0d 1d 04 01 48 c7 c7 60 20 fa 84 e8 9e 8b 0d ff <0f> 0b eb 8d e8 a5 e9 36 ff c6 05 7b 0d 1d 04 01 48 c7 c7 c0 20 fa RSP: 0018:ffff8881e4d8fa70 EFLAGS: 00010246 RAX: 32fe2aea52954b00 RBX: 0000000000000002 RCX: ffff8881d6c20000 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: 0000000000000002 R08: ffffffff814d6db2 R09: ffffed103edc5262 R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000 R13: ffff8881e41a5e80 R14: dffffc0000000000 R15: ffff8881e41a5ea0 FS: 000055558a678500(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff26243113f CR3: 0000000005e0e000 CR4: 00000000003406b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: refcount_add include/linux/refcount.h:192 [inline] refcount_inc include/linux/refcount.h:228 [inline] get_task_struct include/linux/sched/task.h:112 [inline] kthread_stop+0x1a5/0x4a0 kernel/kthread.c:612 ext4_put_super+0x790/0xbb0 fs/ext4/super.c:1055 generic_shutdown_super+0x120/0x300 fs/super.c:464 kill_block_super+0x7a/0xe0 fs/super.c:1455 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 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0xcaf/0x2bc0 kernel/exit.c:861 do_group_exit+0x138/0x300 kernel/exit.c:984 __do_sys_exit_group kernel/exit.c:995 [inline] __se_sys_exit_group kernel/exit.c:993 [inline] __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:993 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 RIP: 0033:0x7ff262431169 Code: Bad RIP value. RSP: 002b:00007ffdbb392e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 00007ff2624b20b1 RCX: 00007ff262431169 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001 RBP: 0000000000000075 R08: 00007ffdbb390c05 R09: 00007ffdbb394120 R10: 000000000000000b R11: 0000000000000246 R12: 00007ffdbb394120 R13: 00007ff2624b208c R14: 000055558a6784a8 R15: 00007ffdbb3951f0 ---[ end trace 6a61b5f69d9bafee ]---