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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:192 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801ca3de018 by task syz-executor5/10849

CPU: 1 PID: 10849 Comm: syz-executor5 Not tainted 4.16.0-rc4+ #264
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+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ip6_dst_idev include/net/ip6_fib.h:192 [inline]
 ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
 inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
 l2tp_xmit_core net/l2tp/l2tp_core.c:1053 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1148
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:639
 SYSC_sendto+0x361/0x5c0 net/socket.c:1748
 SyS_sendto+0x40/0x50 net/socket.c:1716
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f90a14e1c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f90a14e26d4 RCX: 0000000000453e69
RDX: 000000000000100b RSI: 0000000020001180 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 00000000200021c0 R09: 0000000000000080
R10: 0000000000040001 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004ca R14: 00000000006f7390 R15: 0000000000000000

Allocated by task 10429:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
 kmalloc include/linux/slab.h:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 kobject_uevent_env+0x1ed/0xd30 lib/kobject_uevent.c:443
 kobject_uevent+0x1f/0x30 lib/kobject_uevent.c:565
 rx_queue_add_kobject net/core/net-sysfs.c:935 [inline]
 net_rx_queue_update_kobjects+0x3fc/0x590 net/core/net-sysfs.c:954
 register_queue_kobjects net/core/net-sysfs.c:1397 [inline]
 netdev_register_kobject+0x271/0x360 net/core/net-sysfs.c:1608
 register_netdevice+0xa94/0xf70 net/core/dev.c:7908
 ip6mr_reg_vif net/ipv6/ip6mr.c:639 [inline]
 mif6_add net/ipv6/ip6mr.c:842 [inline]
 ip6_mroute_setsockopt+0xb2c/0x1740 net/ipv6/ip6mr.c:1561
 do_ipv6_setsockopt.isra.8+0x2f0/0x39d0 net/ipv6/ipv6_sockglue.c:163
 ipv6_setsockopt+0xd7/0x130 net/ipv6/ipv6_sockglue.c:922
 rawv6_setsockopt+0x4a/0xf0 net/ipv6/raw.c:1060
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2980
 SYSC_setsockopt net/socket.c:1850 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1829
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 10429:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kfree+0xd9/0x260 mm/slab.c:3800
 kobject_uevent_env+0x252/0xd30 lib/kobject_uevent.c:549
 kobject_uevent+0x1f/0x30 lib/kobject_uevent.c:565
 rx_queue_add_kobject net/core/net-sysfs.c:935 [inline]
 net_rx_queue_update_kobjects+0x3fc/0x590 net/core/net-sysfs.c:954
 register_queue_kobjects net/core/net-sysfs.c:1397 [inline]
 netdev_register_kobject+0x271/0x360 net/core/net-sysfs.c:1608
 register_netdevice+0xa94/0xf70 net/core/dev.c:7908
 ip6mr_reg_vif net/ipv6/ip6mr.c:639 [inline]
 mif6_add net/ipv6/ip6mr.c:842 [inline]
 ip6_mroute_setsockopt+0xb2c/0x1740 net/ipv6/ip6mr.c:1561
 do_ipv6_setsockopt.isra.8+0x2f0/0x39d0 net/ipv6/ipv6_sockglue.c:163
 ipv6_setsockopt+0xd7/0x130 net/ipv6/ipv6_sockglue.c:922
 rawv6_setsockopt+0x4a/0xf0 net/ipv6/raw.c:1060
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2980
 SYSC_setsockopt net/socket.c:1850 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1829
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801ca3de980
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2408 bytes to the left of
 4096-byte region [ffff8801ca3de980, ffff8801ca3df980)
The buggy address belongs to the page:
page:ffffea000728f780 count:1 mapcount:0 mapping:ffff8801ca3de980 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801ca3de980 0000000000000000 0000000100000001
raw: ffffea0006a63aa0 ffffea000765dd20 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ca3ddf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801ca3ddf80: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801ca3de000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801ca3de080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801ca3de100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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