bisecting fixing commit since 01364dad1d4577e27a57729d41053f661bb8a5b9 building syzkaller on 84f999d6319b21d9567132bf7ed26507f6d24310 testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0 kernel signature: 2dbbc834c7c6eb10e8aa0e5d4ae61d5348df1d223cef9776fdd17543aa45eaab run #0: crashed: WARNING: held lock freed in pppol2tp_release run #1: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #2: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #3: crashed: WARNING: held lock freed in pppol2tp_release run #4: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #5: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #6: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #7: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #8: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #9: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge testing current HEAD ab9dfda232481dcfaf549ce774004d116fc80c13 testing commit ab9dfda232481dcfaf549ce774004d116fc80c13 with gcc (GCC) 8.1.0 kernel signature: 4b3722abc1def3511dee996d655be8847ebb6f9a109ba64f01f13f9dc4e8047e run #0: crashed: WARNING: held lock freed in pppol2tp_release run #1: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #2: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #3: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #4: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #5: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #6: crashed: WARNING: held lock freed in pppol2tp_release run #7: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #8: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge run #9: crashed: WARNING: held lock freed in pppol2tp_release revisions tested: 2, total time: 26m56.517207422s (build: 19m12.167702261s, test: 6m26.990958721s) the crash still happens on HEAD commit msg: Linux 4.14.180 crash: WARNING: held lock freed in pppol2tp_release l2tp_core: tunl 2: sockfd_lookup(fd=5) returned -9 l2tp_core: tunl 2: sockfd_lookup(fd=5) returned -9 ========================= WARNING: held lock freed! 4.14.180-syzkaller #0 Not tainted ------------------------- syz-executor.5/11640 is freeing memory ffff8880a0cc2980-ffff8880a0cc317f, with a lock still held there! (sk_lock-AF_PPPOX){+.+.}, at: [] lock_sock include/net/sock.h:1467 [inline] (sk_lock-AF_PPPOX){+.+.}, at: [] pppol2tp_release+0x45/0x2a0 net/l2tp/l2tp_ppp.c:476 2 locks held by syz-executor.5/11640: #0: (&sb->s_type->i_mutex_key#13){+.+.}, at: [] inode_lock include/linux/fs.h:719 [inline] #0: (&sb->s_type->i_mutex_key#13){+.+.}, at: [] __sock_release+0x7d/0x2a0 net/socket.c:601 #1: (sk_lock-AF_PPPOX){+.+.}, at: [] lock_sock include/net/sock.h:1467 [inline] #1: (sk_lock-AF_PPPOX){+.+.}, at: [] pppol2tp_release+0x45/0x2a0 net/l2tp/l2tp_ppp.c:476 stack backtrace: CPU: 0 PID: 11640 Comm: syz-executor.5 Not tainted 4.14.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 print_freed_lock_bug kernel/locking/lockdep.c:4463 [inline] debug_check_no_locks_freed.cold.64+0x9e/0xaa kernel/locking/lockdep.c:4496 kfree+0xb1/0x270 mm/slab.c:3812 sk_prot_free net/core/sock.c:1504 [inline] __sk_destruct+0x47f/0x5a0 net/core/sock.c:1581 sk_destruct+0x83/0xb0 net/core/sock.c:1596 __sk_free+0x47/0x1f0 net/core/sock.c:1604 sk_free+0x1a/0x20 net/core/sock.c:1615 sock_put include/net/sock.h:1658 [inline] pppol2tp_release+0x222/0x2a0 net/l2tp/l2tp_ppp.c:493 __sock_release+0xc2/0x2a0 net/socket.c:602 sock_close+0x10/0x20 net/socket.c:1139 __fput+0x232/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x16a/0x1b0 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c849 RSP: 002b:00007f557c473c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: 0000000000000000 RBX: 00007f557c4746d4 RCX: 000000000045c849 RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000004 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000008d R14: 00000000004c324b R15: 000000000076bf0c ================================================================== BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline] BUG: KASAN: use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline] BUG: KASAN: use-after-free in do_raw_spin_lock+0x1ef/0x230 kernel/locking/spinlock_debug.c:112 Read of size 4 at addr ffff8880a0cc2a0c by task syz-executor.5/11640 CPU: 1 PID: 11640 Comm: syz-executor.5 Not tainted 4.14.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 __read_once_size include/linux/compiler.h:183 [inline] debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline] do_raw_spin_lock+0x1ef/0x230 kernel/locking/spinlock_debug.c:112 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline] _raw_spin_lock_bh+0x39/0x40 kernel/locking/spinlock.c:176 spin_lock_bh include/linux/spinlock.h:322 [inline] release_sock+0x1b/0x180 net/core/sock.c:2780 pppol2tp_release+0x1f6/0x2a0 net/l2tp/l2tp_ppp.c:495 __sock_release+0xc2/0x2a0 net/socket.c:602 sock_close+0x10/0x20 net/socket.c:1139 __fput+0x232/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x16a/0x1b0 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c849 RSP: 002b:00007f557c473c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: 0000000000000000 RBX: 00007f557c4746d4 RCX: 000000000045c849 RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000004 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000008d R14: 00000000004c324b R15: 000000000076bf0c Allocated by task 11640: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551 __do_kmalloc mm/slab.c:3720 [inline] __kmalloc+0x15b/0x7b0 mm/slab.c:3729 kmalloc include/linux/slab.h:493 [inline] sk_prot_alloc+0x146/0x240 net/core/sock.c:1467 sk_alloc+0x30/0xc10 net/core/sock.c:1521 pppol2tp_create+0x23/0x1d0 net/l2tp/l2tp_ppp.c:534 pppox_create+0xd3/0x1f0 drivers/net/ppp/pppox.c:134 __sock_create+0x262/0x540 net/socket.c:1275 sock_create net/socket.c:1315 [inline] SYSC_socket net/socket.c:1345 [inline] SyS_socket+0xc6/0x1a0 net/socket.c:1325 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 11640: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 sk_prot_free net/core/sock.c:1504 [inline] __sk_destruct+0x47f/0x5a0 net/core/sock.c:1581 sk_destruct+0x83/0xb0 net/core/sock.c:1596 __sk_free+0x47/0x1f0 net/core/sock.c:1604 sk_free+0x1a/0x20 net/core/sock.c:1615 sock_put include/net/sock.h:1658 [inline] pppol2tp_release+0x222/0x2a0 net/l2tp/l2tp_ppp.c:493 __sock_release+0xc2/0x2a0 net/socket.c:602 sock_close+0x10/0x20 net/socket.c:1139 __fput+0x232/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x16a/0x1b0 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 The buggy address belongs to the object at ffff8880a0cc2980 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 140 bytes inside of 2048-byte region [ffff8880a0cc2980, ffff8880a0cc3180) The buggy address belongs to the page: page:ffffea0002833080 count:1 mapcount:0 mapping:ffff8880a0cc2100 index:0xffff8880a0cc2100 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a0cc2100 ffff8880a0cc2100 0000000100000002 raw: ffffea00027a91a0 ffffea000283f220 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a0cc2900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a0cc2980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880a0cc2a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a0cc2a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a0cc2b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================