================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 Read of size 4 at addr ffff8800b40d6780 by task syz-executor453/4286 CPU: 0 PID: 4286 Comm: syz-executor453 Not tainted 4.4.133-g3f51ea2 #51 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 5abf41b45dba134f ffff8801d88c7b50 ffffffff81e0e4cd ffffea0002d03580 ffff8800b40d6780 0000000000000000 ffff8800b40d6780 ffffffff82f191d0 ffff8801d88c7b88 ffffffff815154cc ffff8800b40d6780 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_address_description+0x6c/0x216 mm/kasan/report.c:252 [] kasan_report_error mm/kasan/report.c:351 [inline] [] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408 [] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428 [] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 [] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509 [] sock_release+0x96/0x1c0 net/socket.c:586 [] sock_close+0x16/0x20 net/socket.c:1037 [] __fput+0x235/0x6f0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x10f/0x190 kernel/task_work.c:115 [] exit_task_work include/linux/task_work.h:21 [inline] [] do_exit+0x9e5/0x26b0 kernel/exit.c:759 [] do_group_exit+0x111/0x330 kernel/exit.c:889 [] SYSC_exit_group kernel/exit.c:900 [inline] [] SyS_exit_group+0x1d/0x20 kernel/exit.c:898 [] entry_SYSCALL_64_fastpath+0x22/0x9e Allocated by task 4284: [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [] set_track mm/kasan/kasan.c:524 [inline] [] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616 [] __kmalloc+0x124/0x310 mm/slub.c:3613 [] kmalloc include/linux/slab.h:481 [inline] [] kzalloc include/linux/slab.h:620 [inline] [] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748 [] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725 [] SYSC_connect+0x1b8/0x300 net/socket.c:1557 [] SyS_connect+0x24/0x30 net/socket.c:1538 [] entry_SYSCALL_64_fastpath+0x22/0x9e Freed by task 4256: [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [] set_track mm/kasan/kasan.c:524 [inline] [] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589 [] slab_free_hook mm/slub.c:1383 [inline] [] slab_free_freelist_hook mm/slub.c:1405 [inline] [] slab_free mm/slub.c:2859 [inline] [] kfree+0xf4/0x310 mm/slub.c:3749 [] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676 [] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline] [] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279 [] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300 [] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421 [] sk_common_release+0x6d/0x300 net/core/sock.c:2680 [] udp_lib_close+0x15/0x20 include/net/udp.h:190 [] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435 [] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424 [] sock_release+0x96/0x1c0 net/socket.c:586 [] sock_close+0x16/0x20 net/socket.c:1037 [] __fput+0x235/0x6f0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x10f/0x190 kernel/task_work.c:115 [] exit_task_work include/linux/task_work.h:21 [inline] [] do_exit+0x9e5/0x26b0 kernel/exit.c:759 [] do_group_exit+0x111/0x330 kernel/exit.c:889 [] SYSC_exit_group kernel/exit.c:900 [inline] [] SyS_exit_group+0x1d/0x20 kernel/exit.c:898 [] entry_SYSCALL_64_fastpath+0x22/0x9e The buggy address belongs to the object at ffff8800b40d6780 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8800b40d6780, ffff8800b40d6980) The buggy address belongs to the page: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 4319 at kernel/locking/lockdep.c:3123 __lock_acquire+0x23b8/0x5270 kernel/locking/lockdep.c:3123() DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)