bisecting fixing commit since f6e27dbb1afabcba436e346d6aa88a592a1436bb building syzkaller on e38a6630eb6b89a4b3c344dc62ecb3b60f078028 testing commit f6e27dbb1afabcba436e346d6aa88a592a1436bb with gcc (GCC) 8.1.0 kernel signature: 152945e4689d74530bdad47312bfbd8ef38ded8de0913b6ed433b9d201e43651 run #0: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #1: crashed: KASAN: use-after-free Read in l2tp_session_create run #2: crashed: KASAN: use-after-free Read in l2tp_session_create run #3: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #4: crashed: KASAN: use-after-free Read in l2tp_session_create run #5: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #6: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #7: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #8: crashed: KASAN: use-after-free Read in lock_sock_nested run #9: crashed: KASAN: use-after-free Read in pppol2tp_session_close testing current HEAD 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 testing commit 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 with gcc (GCC) 8.1.0 kernel signature: ea20444bb7e662a5c5110bbb616a8317fd7c5cd1f66c70e01d1cd58065e57067 run #0: crashed: KASAN: use-after-free Read in l2tp_session_create run #1: crashed: KASAN: use-after-free Read in lock_sock_nested run #2: crashed: KASAN: use-after-free Read in l2tp_session_create run #3: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #4: crashed: KASAN: use-after-free Read in lock_sock_nested run #5: crashed: KASAN: use-after-free Write in pppol2tp_connect run #6: crashed: KASAN: use-after-free Read in lock_sock_nested run #7: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #8: crashed: KASAN: use-after-free Read in l2tp_session_create run #9: crashed: KASAN: use-after-free Read in pppol2tp_session_close revisions tested: 2, total time: 24m5.29747367s (build: 16m22.388680566s, test: 6m48.606577829s) the crash still happens on HEAD commit msg: Linux 4.14.171 crash: KASAN: use-after-free Read in pppol2tp_session_close l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9 l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9 l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9 l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9 ================================================================== BUG: KASAN: use-after-free in inet_shutdown+0x287/0x300 net/ipv4/af_inet.c:816 Read of size 4 at addr ffff888087dd6600 by task syz-executor.5/9997 CPU: 0 PID: 9997 Comm: syz-executor.5 Not tainted 4.14.171-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 inet_shutdown+0x287/0x300 net/ipv4/af_inet.c:816 pppol2tp_session_close+0x91/0xc0 net/l2tp/l2tp_ppp.c:441 l2tp_tunnel_closeall+0x1df/0x2f0 net/l2tp/l2tp_core.c:1345 l2tp_udp_encap_destroy+0x7d/0xc0 net/l2tp/l2tp_core.c:1371 udpv6_destroy_sock+0x89/0xb0 net/ipv6/udp.c:1444 sk_common_release+0x5e/0x2c0 net/core/sock.c:2989 udp_lib_close+0x9/0x10 include/net/udp.h:203 inet_release+0xd9/0x1c0 net/ipv4/af_inet.c:425 inet6_release+0x46/0x60 net/ipv6/af_inet6.c:450 __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: 0033:0x459a29 RSP: 002b:00007f9c7f074c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000459a29 RDX: 0000000000000026 RSI: 0000000020000180 RDI: 0000000000000005 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9c7f0756d4 R13: 00000000004bff90 R14: 00000000004d1f00 R15: 00000000ffffffff Allocated by task 10003: 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 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 kmem_cache_alloc+0x12e/0x790 mm/slab.c:3552 sock_alloc_inode+0x18/0x230 net/socket.c:251 alloc_inode+0x56/0x150 fs/inode.c:209 new_inode_pseudo+0xc/0xd0 fs/inode.c:898 sock_alloc+0x3c/0x280 net/socket.c:569 __sock_create+0x7a/0x540 net/socket.c:1239 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 9990: 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] kmem_cache_free+0x80/0x2d0 mm/slab.c:3758 sock_destroy_inode+0x50/0x60 net/socket.c:281 destroy_inode+0xb3/0x100 fs/inode.c:266 evict+0x36f/0x590 fs/inode.c:571 iput_final fs/inode.c:1523 [inline] iput+0x3ac/0x810 fs/inode.c:1550 dentry_unlink_inode+0x23e/0x2f0 fs/dcache.c:387 __dentry_kill+0x2d2/0x540 fs/dcache.c:591 dentry_kill fs/dcache.c:632 [inline] dput.part.27+0x49a/0x610 fs/dcache.c:847 dput+0xe/0x20 fs/dcache.c:810 __fput+0x3f7/0x750 fs/file_table.c:228 ____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 ffff888087dd6600 which belongs to the cache sock_inode_cache of size 992 The buggy address is located 0 bytes inside of 992-byte region [ffff888087dd6600, ffff888087dd69e0) The buggy address belongs to the page: page:ffffea00021f7580 count:1 mapcount:0 mapping:ffff888087dd6180 index:0xffff888087dd6ffd flags: 0x1fffc0000000100(slab) raw: 01fffc0000000100 ffff888087dd6180 ffff888087dd6ffd 0000000100000003 raw: ffffea00021f7560 ffffea00021f75e0 ffff88821b75e6c0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888087dd6500: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff888087dd6580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888087dd6600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888087dd6680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888087dd6700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================