================================================================== BUG: KASAN: use-after-free in pppol2tp_connect+0x160a/0x1910 net/l2tp/l2tp_ppp.c:735 Read of size 8 at addr ffff8800b9248410 by task syz-executor7/16384 CPU: 0 PID: 16384 Comm: syz-executor7 Not tainted 4.4.153-g5e24b4e #90 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 bcb194d9d7a83b9e ffff8801bc6afb28 ffffffff81e162ed ffffea0002e49200 ffff8800b9248410 0000000000000000 ffff8800b9248410 ffff8801bc6afd50 ffff8801bc6afb60 ffffffff8151b4d9 ffff8800b9248410 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_load8_noabort+0x14/0x20 mm/kasan/report.c:429 [] pppol2tp_connect+0x160a/0x1910 net/l2tp/l2tp_ppp.c:735 [] SYSC_connect+0x1b8/0x300 net/socket.c:1570 [] SyS_connect+0x24/0x30 net/socket.c:1551 [] entry_SYSCALL_64_fastpath+0x22/0x9e Allocated by task 16384: [] 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:1570 [] SyS_connect+0x24/0x30 net/socket.c:1551 [] entry_SYSCALL_64_fastpath+0x22/0x9e Freed by task 16374: [] 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] [] pppol2tp_session_destruct+0xd7/0x110 net/l2tp/l2tp_ppp.c:477 [] sk_destruct+0x4c/0x4c0 net/core/sock.c:1447 [] __sk_free+0x4f/0x220 net/core/sock.c:1480 [] sk_free+0x30/0x40 net/core/sock.c:1491 [] sock_put include/net/sock.h:1639 [inline] [] pppol2tp_release+0x26a/0x310 net/l2tp/l2tp_ppp.c:518 [] __sock_release+0xd9/0x260 net/socket.c:592 [] sock_close+0x19/0x20 net/socket.c:1050 [] __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 [] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:253 [] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline] [] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349 [] int_ret_from_sys_call+0x25/0xa3 The buggy address belongs to the object at ffff8800b9248280 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff8800b9248280, ffff8800b9248480) The buggy address belongs to the page: PANIC: double fault, error_code: 0x0 CPU: 0 PID: 16384 Comm: syz-executor7 Not tainted 4.4.153-g5e24b4e #90 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8800ac47b000 task.stack: ffff8801bc6a8000 RIP: 0010:[] [] dump_page_badflags+0x6/0x70 mm/debug.c:84 RSP: 0018:ffff880100000000 EFLAGS: 00010046 RAX: 0000000000040000 RBX: ffffea0002e49200 RCX: ffffc900028aa000 RDX: 0000000000000000 RSI: ffffffff83aaae60 RDI: ffffea0002e49200 RBP: ffff880100000008 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: ffffffff858f0274 R12: 0000000000000000 R13: ffffffff83aaae60 R14: ffff8800b9248280 R15: ffff8800b9248480 FS: 00007fc198a07700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8800fffffff8 CR3: 00000000ba0ef000 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: Call Trace: Code: 48 69 c0 80 06 00 00 f0 48 ff 80 68 5c 9f 84 5b 5d c3 48 89 df e8 1b e5 06 00 eb dd 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 <41> 56 41 55 49 89 f5 41 54 49 89 d4 53 48 89 fb 48 83 ec 08 e8