================================================================== 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 ffff8881e8430020 by task syz-executor.3/323 CPU: 0 PID: 323 Comm: syz-executor.3 Tainted: G W 5.4.233-syzkaller-00011-g0108362f3305 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 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+0x7a1/0xbc0 fs/ext4/super.c:1055 generic_shutdown_super+0x121/0x2a0 fs/super.c:464 kill_block_super+0x7a/0xe0 fs/super.c:1444 deactivate_locked_super+0xa8/0x110 fs/super.c:335 deactivate_super+0x1e2/0x2a0 fs/super.c:366 cleanup_mnt+0x419/0x4d0 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+0x18b/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 Allocated by task 2: save_stack mm/kasan/common.c:70 [inline] set_track mm/kasan/common.c:78 [inline] __kasan_kmalloc+0x130/0x1d0 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+0xd0/0x220 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:874 copy_process+0x56d/0x3230 kernel/fork.c:1881 _do_fork+0x197/0x900 kernel/fork.c:2396 kernel_thread+0x16a/0x1d0 kernel/fork.c:2486 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 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+0x178/0x230 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+0xd5/0x290 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+0x22e/0x630 kernel/softirq.c:292 The buggy address belongs to the object at ffff8881e8430000 which belongs to the cache task_struct of size 3904 The buggy address is located 32 bytes inside of 3904-byte region [ffff8881e8430000, ffff8881e8430f40) The buggy address belongs to the page: page:ffffea0007a10c00 refcount:1 mapcount:0 mapping:ffff8881f5cecc80 index:0x0 compound_mapcount: 0 flags: 0x8000000000010200(slab|head) raw: 8000000000010200 ffffea0006ba7200 0000000200000002 ffff8881f5cecc80 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+0x2ce8/0x2d70 mm/page_alloc.c:3794 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4891 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+0x5a/0x90 mm/slub.c:2707 slab_alloc_node mm/slub.c:2792 [inline] slab_alloc mm/slub.c:2837 [inline] kmem_cache_alloc+0x100/0x220 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:874 copy_process+0x56d/0x3230 kernel/fork.c:1881 _do_fork+0x197/0x900 kernel/fork.c:2396 __do_sys_clone kernel/fork.c:2554 [inline] __se_sys_clone kernel/fork.c:2535 [inline] __x64_sys_clone+0x26b/0x2c0 kernel/fork.c:2535 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 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+0x83d/0x940 mm/page_alloc.c:1438 free_the_page mm/page_alloc.c:4953 [inline] __free_pages+0x91/0x140 mm/page_alloc.c:4959 __free_slab+0x221/0x2e0 mm/slub.c:1774 free_slab mm/slub.c:1789 [inline] discard_slab mm/slub.c:1795 [inline] unfreeze_partials+0x14e/0x180 mm/slub.c:2288 put_cpu_partial+0xb4/0x150 mm/slub.c:2324 __slab_free+0x288/0x350 mm/slub.c:2971 qlist_free_all+0x43/0xb0 mm/kasan/quarantine.c:167 quarantine_reduce+0x174/0x190 mm/kasan/quarantine.c:260 __kasan_kmalloc+0x43/0x1d0 mm/kasan/common.c:507 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+0xd0/0x220 mm/slub.c:2842 getname_flags+0xb8/0x4e0 fs/namei.c:141 user_path_at_empty+0x28/0x50 fs/namei.c:2683 user_path_at include/linux/namei.h:49 [inline] vfs_statx+0x115/0x210 fs/stat.c:187 vfs_fstatat include/linux/fs.h:3372 [inline] __do_sys_newfstatat fs/stat.c:367 [inline] __se_sys_newfstatat+0xce/0x770 fs/stat.c:361 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 Memory state around the buggy address: ffff8881e842ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881e842ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8881e8430000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881e8430080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881e8430100: 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: 323 at lib/refcount.c:25 refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Modules linked in: CPU: 1 PID: 323 Comm: syz-executor.3 Tainted: G B W 5.4.233-syzkaller-00011-g0108362f3305 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 RIP: 0010:refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25 Code: 03 01 48 c7 c7 c0 7f d9 84 e8 aa 8a 19 ff 0f 0b eb a9 e8 c1 a9 41 ff c6 05 b1 40 e3 03 01 48 c7 c7 40 80 d9 84 e8 8e 8a 19 ff <0f> 0b eb 8d e8 a5 a9 41 ff c6 05 96 40 e3 03 01 48 c7 c7 a0 80 d9 RSP: 0018:ffff8881af27fc30 EFLAGS: 00010246 RAX: d459d9b05cf5d900 RBX: 0000000000000002 RCX: ffff8881de0c6e40 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: 0000000000000002 R08: ffffffff814ca536 R09: ffffed103edeaa08 R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000 R13: ffff8881e8430000 R14: dffffc0000000000 R15: ffff8881e8430020 FS: 000055555589a400(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc550dfeb8 CR3: 00000001af246000 CR4: 00000000003406e0 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+0x7a1/0xbc0 fs/ext4/super.c:1055 generic_shutdown_super+0x121/0x2a0 fs/super.c:464 kill_block_super+0x7a/0xe0 fs/super.c:1444 deactivate_locked_super+0xa8/0x110 fs/super.c:335 deactivate_super+0x1e2/0x2a0 fs/super.c:366 cleanup_mnt+0x419/0x4d0 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+0x18b/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 ---[ end trace af50fdb9ad066b5f ]---