================================================================== 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:111 [inline] BUG: KASAN: use-after-free in kthread_stop+0x32/0x460 kernel/kthread.c:612 Write of size 4 at addr ffff8881e50a0fe0 by task syz-executor.4/320 CPU: 0 PID: 320 Comm: syz-executor.4 Not tainted 5.4.219-syzkaller-00097-ga76dfbc99260 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1d8/0x241 lib/dump_stack.c:118 print_address_description+0x8c/0x630 mm/kasan/report.c:384 __kasan_report+0xf6/0x130 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+0x298/0x2d0 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:111 [inline] kthread_stop+0x32/0x460 kernel/kthread.c:612 ext4_put_super+0x789/0xbc0 fs/ext4/super.c:1055 generic_shutdown_super+0x11b/0x2a0 fs/super.c:464 kill_block_super+0x79/0xd0 fs/super.c:1444 deactivate_locked_super+0xaf/0x100 fs/super.c:335 deactivate_super+0x1b3/0x270 fs/super.c:366 cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102 task_work_run+0x186/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x1ba/0x1d0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x17c/0x1d0 arch/x86/entry/common.c:194 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 Allocated by task 2: save_stack mm/kasan/common.c:70 [inline] set_track mm/kasan/common.c:78 [inline] __kasan_kmalloc+0x131/0x1e0 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+0xd0/0x210 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/0x5a0 kernel/fork.c:871 copy_process+0x56e/0x3230 kernel/fork.c:1878 _do_fork+0x196/0x8d0 kernel/fork.c:2391 kernel_thread+0x169/0x1d0 kernel/fork.c:2481 create_kthread kernel/kthread.c:311 [inline] kthreadd+0x3cd/0x520 kernel/kthread.c:654 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354 Freed by task 16: 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+0x178/0x240 mm/kasan/common.c:487 slab_free_hook mm/slub.c:1455 [inline] slab_free_freelist_hook+0x80/0x150 mm/slub.c:1494 slab_free mm/slub.c:3080 [inline] kmem_cache_free+0xa9/0x1d0 mm/slub.c:3096 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x49e/0xa10 kernel/rcu/tree.c:2167 rcu_core+0x4ba/0xca0 kernel/rcu/tree.c:2387 __do_softirq+0x23e/0x643 kernel/softirq.c:292 The buggy address belongs to the object at ffff8881e50a0fc0 which belongs to the cache task_struct of size 3904 The buggy address is located 32 bytes inside of 3904-byte region [ffff8881e50a0fc0, ffff8881e50a1f00) The buggy address belongs to the page: page:ffffea0007942800 refcount:1 mapcount:0 mapping:ffff8881f5cec780 index:0xffff8881e50a2f40 compound_mapcount: 0 flags: 0x8000000000010200(slab|head) raw: 8000000000010200 0000000000000000 0000000100000001 ffff8881f5cec780 raw: ffff8881e50a2f40 0000000080080006 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+0x194/0x380 mm/page_alloc.c:2171 get_page_from_freelist+0x524/0x560 mm/page_alloc.c:3794 __alloc_pages_nodemask+0x372/0x860 mm/page_alloc.c:4891 alloc_slab_page+0x39/0x3e0 mm/slub.c:343 allocate_slab mm/slub.c:1683 [inline] new_slab+0x97/0x450 mm/slub.c:1749 new_slab_objects mm/slub.c:2505 [inline] ___slab_alloc+0x320/0x4a0 mm/slub.c:2667 __slab_alloc+0x5a/0x90 mm/slub.c:2707 slab_alloc_node mm/slub.c:2792 [inline] slab_alloc mm/slub.c:2837 [inline] kmem_cache_alloc+0x100/0x210 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/0x5a0 kernel/fork.c:871 copy_process+0x56e/0x3230 kernel/fork.c:1878 _do_fork+0x196/0x8d0 kernel/fork.c:2391 kernel_thread+0x169/0x1d0 kernel/fork.c:2481 create_kthread kernel/kthread.c:311 [inline] kthreadd+0x3cd/0x520 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+0x7fe/0x930 mm/page_alloc.c:1438 free_the_page mm/page_alloc.c:4953 [inline] __free_pages+0x8f/0x250 mm/page_alloc.c:4959 __free_slab+0x22b/0x2e0 mm/slub.c:1774 free_slab mm/slub.c:1789 [inline] discard_slab mm/slub.c:1795 [inline] unfreeze_partials+0x14f/0x180 mm/slub.c:2288 put_cpu_partial+0xb5/0x150 mm/slub.c:2324 __slab_free+0x2ac/0x370 mm/slub.c:2971 qlist_free_all+0x4c/0xb0 mm/kasan/quarantine.c:167 quarantine_reduce+0x174/0x190 mm/kasan/quarantine.c:260 __kasan_kmalloc+0x43/0x1e0 mm/kasan/common.c:507 kmalloc include/linux/slab.h:556 [inline] kzalloc include/linux/slab.h:690 [inline] mb_cache_create+0x5e/0x500 fs/mbcache.c:350 ext4_fill_super+0x6b71/0x8ce0 fs/ext4/super.c:4538 mount_bdev+0x22d/0x340 fs/super.c:1417 legacy_get_tree+0xde/0x170 fs/fs_context.c:647 vfs_get_tree+0x85/0x260 fs/super.c:1547 do_new_mount+0x299/0x580 fs/namespace.c:2843 do_mount+0x6ac/0xe10 fs/namespace.c:3163 Memory state around the buggy address: ffff8881e50a0e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881e50a0f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >ffff8881e50a0f80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8881e50a1000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881e50a1080: 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: 320 at lib/refcount.c:25 refcount_warn_saturate+0x13d/0x1a0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 320 Comm: syz-executor.4 Tainted: G B 5.4.219-syzkaller-00097-ga76dfbc99260 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 RIP: 0010:refcount_warn_saturate+0x13d/0x1a0 lib/refcount.c:25 Code: c7 a0 ff fd 84 31 c0 e8 91 76 15 ff 0f 0b eb a3 e8 78 9d 3e ff c6 05 08 27 fe 03 01 48 c7 c7 20 00 fe 84 31 c0 e8 73 76 15 ff <0f> 0b eb 85 e8 5a 9d 3e ff c6 05 eb 26 fe 03 01 48 c7 c7 80 00 fe RSP: 0018:ffff8881abfcfc50 EFLAGS: 00010246 RAX: f599026447074e00 RBX: 0000000000000002 RCX: ffff8881de0d4ec0 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: 0000000000000002 R08: ffffffff814e3a77 R09: ffffed103edcaa08 R10: ffffed103edcaa08 R11: 1ffff1103edcaa07 R12: dffffc0000000000 R13: ffff8881e50a0fc0 R14: dffffc0000000000 R15: ffff8881e50a0fe0 FS: 0000555555bd9400(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe4ec6f0718 CR3: 00000001abf9a000 CR4: 00000000003426f0 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:111 [inline] kthread_stop+0x1a1/0x460 kernel/kthread.c:612 ext4_put_super+0x789/0xbc0 fs/ext4/super.c:1055 generic_shutdown_super+0x11b/0x2a0 fs/super.c:464 kill_block_super+0x79/0xd0 fs/super.c:1444 deactivate_locked_super+0xaf/0x100 fs/super.c:335 deactivate_super+0x1b3/0x270 fs/super.c:366 cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102 task_work_run+0x186/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x1ba/0x1d0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x17c/0x1d0 arch/x86/entry/common.c:194 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 ---[ end trace a8c31ee77deee411 ]---