audit: type=1400 audit(1521268324.751:50): avc: denied { create } for pid=11661 comm="syz-executor6" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_iscsi_socket permissive=1 ================================================================== BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476 Read of size 4 at addr ffff8801d327b180 by task syz-executor3/11696 CPU: 0 PID: 11696 Comm: syz-executor3 Not tainted 4.4.120-gd63fdf6 #29 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 78d6e0bf637c26b9 ffff8801d04bfc20 ffffffff81d0408d ffffea00074c9e80 ffff8801d327b180 0000000000000000 ffff8801d327b180 ffffffff82de7d30 ffff8801d04bfc58 ffffffff814fe143 ffff8801d327b180 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_address_description+0x73/0x260 mm/kasan/report.c:252 [] kasan_report_error mm/kasan/report.c:351 [inline] [] kasan_report+0x285/0x370 mm/kasan/report.c:408 [] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428 [] pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476 [] sk_destruct+0x4a/0x4c0 net/core/sock.c:1447 [] __sk_free+0x57/0x230 net/core/sock.c:1480 [] sk_free+0x30/0x40 net/core/sock.c:1491 [] sock_put include/net/sock.h:1639 [inline] [] pppol2tp_release+0x27a/0x310 net/l2tp/l2tp_ppp.c:518 [] sock_release+0x8d/0x1e0 net/socket.c:586 [] sock_close+0x16/0x20 net/socket.c:1037 [] __fput+0x233/0x6d0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x104/0x180 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:252 [] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline] [] syscall_return_slowpath arch/x86/entry/common.c:348 [inline] [] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline] [] do_fast_syscall_32+0x614/0x8a0 arch/x86/entry/common.c:459 [] sysenter_flags_fixed+0xd/0x17 Allocated by task 11696: [] 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+0xad/0xe0 mm/kasan/kasan.c:616 [] __kmalloc+0x124/0x320 mm/slub.c:3613 [] kmalloc include/linux/slab.h:481 [inline] [] kzalloc include/linux/slab.h:620 [inline] [] l2tp_session_create+0x39/0x10f0 net/l2tp/l2tp_core.c:1744 [] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718 [] SYSC_connect+0x1b6/0x310 net/socket.c:1557 [] SyS_connect+0x24/0x30 net/socket.c:1538 [] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline] [] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459 [] sysenter_flags_fixed+0xd/0x17 Freed by task 11699: [] 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+0xfc/0x300 mm/slub.c:3749 [] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1672 [] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline] [] l2tp_tunnel_closeall+0x2d1/0x3b0 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+0x6b/0x300 net/core/sock.c:2680 [] udp_lib_close+0x15/0x20 include/net/udp.h:190 [] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435 [] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424 [] sock_release+0x8d/0x1e0 net/socket.c:586 [] sock_close+0x16/0x20 net/socket.c:1037 [] __fput+0x233/0x6d0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x104/0x180 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:252 [] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline] [] syscall_return_slowpath arch/x86/entry/common.c:348 [inline] [] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline] [] do_fast_syscall_32+0x614/0x8a0 arch/x86/entry/common.c:459 [] sysenter_flags_fixed+0xd/0x17 The buggy address belongs to the object at ffff8801d327b180 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8801d327b180, ffff8801d327b380) The buggy address belongs to the page: ------------[ cut here ]------------ BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 80000001cb2d8067 PUD 1d4f3f067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 11673 Comm: syz-executor1 Not tainted 4.4.120-gd63fdf6 #29 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8800b51de000 task.stack: ffff8801d2ca0000 RIP: 0010:[<0000000000000000>] [< (null)>] (null) RSP: 0018:ffff8801db307df0 EFLAGS: 00010006 RAX: ffff8800b51de000 RBX: ffff8801cdbb2690 RCX: ffffffff812ad920 RDX: 0000000000010000 RSI: ffffffff842bdb60 RDI: ffff8801cdbb2690 RBP: ffff8801db307ee0 R08: 1ffff1003b431db5 R09: 0000000000000001 R10: 0000000000000000 R11: 1ffff1003b660f6a R12: 0000000000000000 R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8801db319640 FS: 0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f6f1fb40 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000001d47c6000 CR4: 0000000000160670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff812ad926 ffff88021fffd057 ffff88021fffd05b ffff88021fffd04f 1ffff1003b660fcb ffff8801db3196a0 ffffed003b660fca ffff8801db319780 0303fc0000000001 ffff8801db319678 ffffed003b6632d4 ffff8801db319798 Call Trace: [] hrtimer_interrupt+0x1a6/0x440 kernel/time/hrtimer.c:1358 [] local_apic_timer_interrupt+0x6a/0xb0 arch/x86/kernel/apic/apic.c:901 [] smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:925 [] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:737 [] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline] [] finish_wait+0xfa/0x180 kernel/sched/wait.c:253 [] wait_for_more_packets net/core/datagram.c:121 [inline] [] __skb_recv_datagram+0xe84/0x1560 net/core/datagram.c:256 [] unix_dgram_recvmsg+0x21b/0xdb0 net/unix/af_unix.c:2133 [] sock_recvmsg_nosec+0x70/0x90 net/socket.c:727 [] ___sys_recvmsg+0x26d/0x560 net/socket.c:2116 [] __sys_recvmmsg+0x3b8/0x6f0 net/socket.c:2216 [] C_SYSC_recvmmsg net/compat.c:755 [inline] [] compat_SyS_recvmmsg+0x146/0x160 net/compat.c:747 [] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline] [] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459 [] sysenter_flags_fixed+0xd/0x17 Code: Bad RIP value. RIP [< (null)>] (null) RSP CR2: 0000000000000000 ---[ end trace 60c6540feccba65e ]---