netlink: 3 bytes leftover after parsing attributes in process `syz-executor7'. audit: type=1400 audit(1519876908.908:21): avc: denied { getattr } for pid=6366 comm="syz-executor5" path="socket:[16412]" dev="sockfs" ino=16412 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1 ================================================================== BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:243 [inline] BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1695 [inline] BUG: KASAN: use-after-free in pppol2tp_connect+0x18a9/0x18f0 net/l2tp/l2tp_ppp.c:739 Read of size 8 at addr ffff8801b6c0f058 by task syz-executor1/6376 CPU: 0 PID: 6376 Comm: syz-executor1 Not tainted 4.9.85-g6e463bb #54 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d47e7ac0 ffffffff81d955d9 ffffea0006db0200 ffff8801b6c0f058 0000000000000000 ffff8801b6c0f058 1ffff1003a8fcf75 ffff8801d47e7af8 ffffffff8153e0c3 ffff8801b6c0f058 0000000000000008 0000000000000000 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] print_address_description+0x73/0x280 mm/kasan/report.c:252 [] kasan_report_error mm/kasan/report.c:351 [inline] [] kasan_report+0x275/0x360 mm/kasan/report.c:408 [] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429 [] __read_once_size include/linux/compiler.h:243 [inline] [] sk_dst_get include/net/sock.h:1695 [inline] [] pppol2tp_connect+0x18a9/0x18f0 net/l2tp/l2tp_ppp.c:739 [] SYSC_connect+0x1b6/0x310 net/socket.c:1562 [] SyS_connect+0x24/0x30 net/socket.c:1543 [] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] [] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 [] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 Allocated by task 5866: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack+0x43/0xd0 mm/kasan/kasan.c:505 set_track mm/kasan/kasan.c:517 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:609 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547 slab_post_alloc_hook mm/slab.h:417 [inline] slab_alloc_node mm/slub.c:2715 [inline] slab_alloc mm/slub.c:2723 [inline] kmem_cache_alloc+0xba/0x290 mm/slub.c:2728 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1332 sk_alloc+0x3a/0x3a0 net/core/sock.c:1394 inet6_create+0x2c8/0xde0 net/ipv6/af_inet6.c:198 __sock_create+0x3ab/0x640 net/socket.c:1182 sock_create net/socket.c:1222 [inline] SYSC_socket net/socket.c:1252 [inline] SyS_socket+0xf0/0x1b0 net/socket.c:1232 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 Freed by task 5900: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack+0x43/0xd0 mm/kasan/kasan.c:505 set_track mm/kasan/kasan.c:517 [inline] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582 slab_free_hook mm/slub.c:1355 [inline] slab_free_freelist_hook mm/slub.c:1377 [inline] slab_free mm/slub.c:2958 [inline] kmem_cache_free+0xc7/0x300 mm/slub.c:2980 sk_prot_free net/core/sock.c:1375 [inline] __sk_destruct+0x3c9/0x570 net/core/sock.c:1455 __rcu_reclaim kernel/rcu/rcu.h:118 [inline] rcu_do_batch kernel/rcu/tree.c:2789 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline] rcu_process_callbacks+0x898/0x1300 kernel/rcu/tree.c:3037 __do_softirq+0x206/0x951 kernel/softirq.c:284 The buggy address belongs to the object at ffff8801b6c0ee80 which belongs to the cache UDPv6 of size 1496 The buggy address is located 472 bytes inside of 1496-byte region [ffff8801b6c0ee80, ffff8801b6c0f458) The buggy address belongs to the page: page:ffffea0006db0200 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 flags: 0x8000000000004080(slab|head) page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801b6c0ef00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b6c0ef80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8801b6c0f000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801b6c0f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b6c0f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================