bisecting fixing commit since e1f7d50ae3a3ec342e87a9b1ce6787bfb8b3c08b building syzkaller on af6b8ef8f18c45343685f0ee7af9dd3a4b2b5d95 testing commit e1f7d50ae3a3ec342e87a9b1ce6787bfb8b3c08b with gcc (GCC) 8.1.0 kernel signature: 14ee72cfab7e1e74efc1c7ab6e8a0b49955e4921b5908779fa6014c0003a6713 run #0: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #1: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #2: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #3: crashed: KASAN: use-after-free Read in lock_sock_nested run #4: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #5: crashed: KASAN: use-after-free Read in lock_sock_nested 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 pppol2tp_session_close run #9: crashed: KASAN: use-after-free Read in lock_sock_nested testing current HEAD 9a95f25269bd9257ab9fba7bb14355d50b5f39ec testing commit 9a95f25269bd9257ab9fba7bb14355d50b5f39ec with gcc (GCC) 8.1.0 kernel signature: 87aa0400e8fc30c6a97967f771c47776903d8561a69e0dead6743c19b3d7a6ba run #0: crashed: KASAN: use-after-free Read in lock_sock_nested run #1: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #2: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #3: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #4: crashed: KASAN: use-after-free Read in pppol2tp_session_close run #5: crashed: KASAN: use-after-free Read in __lock_sock 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 pppol2tp_session_close run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount revisions tested: 2, total time: 29m17.971542704s (build: 17m54.699132164s, test: 10m34.034940633s) the crash still happens on HEAD commit msg: Linux 4.14.168 crash: KASAN: use-after-free Write in ex_handler_refcount l2tp_core: tunl 4: sockfd_lookup(fd=3) returned -9 l2tp_core: tunl 4: sockfd_lookup(fd=3) returned -9 ================================================================== BUG: KASAN: use-after-free in ex_handler_refcount+0x141/0x180 arch/x86/mm/extable.c:49 Write of size 4 at addr ffff88808afa227c by task syz-executor.5/17439 CPU: 1 PID: 17439 Comm: syz-executor.5 Not tainted 4.14.168-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_store4_noabort+0x17/0x20 mm/kasan/report.c:434 ex_handler_refcount+0x141/0x180 arch/x86/mm/extable.c:49 fixup_exception+0x7c/0xb3 arch/x86/mm/extable.c:197 do_trap_no_signal arch/x86/kernel/traps.c:208 [inline] do_trap+0x63/0x240 arch/x86/kernel/traps.c:257 do_error_trap+0x159/0x310 arch/x86/kernel/traps.c:301 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963 RIP: 0010:inat_get_avx_attribute+0x3a31/0x7591 RSP: 0018:ffff888085887d58 EFLAGS: 00010296 RAX: 0000000000000000 RBX: ffff88808afa2040 RCX: ffff88808afa227c RDX: 0000000000000004 RSI: ffff8880a83cada8 RDI: ffff88808afa2040 RBP: ffff888085887d58 R08: ffff8880a83cadc8 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff888093c82c80 R13: ffff888090de5060 R14: ffff88808afa23a0 R15: ffffffff87667360 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: 0033:0x45a919 RSP: 002b:00007f5ced2e7c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000045a919 RDX: 0000000000000032 RSI: 00000000200001c0 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5ced2e86d4 R13: 00000000004c10c5 R14: 00000000004d4ec8 R15: 00000000ffffffff Allocated by task 17483: 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 17430: 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_session_sock_put+0x49/0x60 net/l2tp/l2tp_ppp.c:271 l2tp_tunnel_closeall+0x208/0x2f0 net/l2tp/l2tp_core.c:1343 l2tp_udp_encap_destroy+0x79/0xb0 net/l2tp/l2tp_core.c:1366 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 The buggy address belongs to the object at ffff88808afa2040 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 572 bytes inside of 2048-byte region [ffff88808afa2040, ffff88808afa2840) The buggy address belongs to the page: page:ffffea00022be880 count:1 mapcount:0 mapping:ffff88808afa2040 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff88808afa2040 0000000000000000 0000000100000003 raw: ffffea0002156720 ffffea00025a81a0 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88808afa2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808afa2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88808afa2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88808afa2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808afa2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================