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BUG: KASAN: use-after-free in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
Read of size 2 at addr ffff8801ca01658b by task syz-executor2/5915

CPU: 1 PID: 5915 Comm: syz-executor2 Not tainted 4.15.0+ #287
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+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
 erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
 erspan_xmit+0x3b8/0x13b0 net/ipv4/ip_gre.c:740
 __netdev_start_xmit include/linux/netdevice.h:4042 [inline]
 netdev_start_xmit include/linux/netdevice.h:4051 [inline]
 packet_direct_xmit+0x315/0x6b0 net/packet/af_packet.c:266
 packet_snd net/packet/af_packet.c:2943 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2968
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:648
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007f2fe9dd6c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299
RDX: 0000000000000000 RSI: 0000000020015f41 RDI: 0000000000000013
RBP: 000000000000059d R08: 0000000020015fec R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7758
R13: 00000000ffffffff R14: 00007f2fe9dd76d4 R15: 0000000000000000

Allocated by task 2651:
 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:551
 __do_kmalloc_node mm/slab.c:3672 [inline]
 __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3686
 __kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
 __alloc_skb+0x13b/0x780 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:983 [inline]
 netlink_dump+0x28c/0xcf0 net/netlink/af_netlink.c:2164
 netlink_recvmsg+0x9bf/0x1300 net/netlink/af_netlink.c:1947
 sock_recvmsg_nosec net/socket.c:811 [inline]
 sock_recvmsg+0xc9/0x110 net/socket.c:818
 ___sys_recvmsg+0x2a4/0x640 net/socket.c:2187
 __sys_recvmsg+0xe2/0x210 net/socket.c:2232
 SYSC_recvmsg net/socket.c:2244 [inline]
 SyS_recvmsg+0x2d/0x50 net/socket.c:2239
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 2651:
 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:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 skb_free_head+0x74/0xb0 net/core/skbuff.c:550
 skb_release_data+0x58c/0x790 net/core/skbuff.c:570
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 consume_skb+0x153/0x490 net/core/skbuff.c:701
 skb_free_datagram+0x1a/0xe0 net/core/datagram.c:331
 netlink_recvmsg+0x5cf/0x1300 net/netlink/af_netlink.c:1943
 sock_recvmsg_nosec net/socket.c:811 [inline]
 sock_recvmsg+0xc9/0x110 net/socket.c:818
 ___sys_recvmsg+0x2a4/0x640 net/socket.c:2187
 __sys_recvmsg+0xe2/0x210 net/socket.c:2232
 SYSC_recvmsg net/socket.c:2244 [inline]
 SyS_recvmsg+0x2d/0x50 net/socket.c:2239
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801ca014080
 which belongs to the cache kmalloc-32768 of size 32768
The buggy address is located 9483 bytes inside of
 32768-byte region [ffff8801ca014080, ffff8801ca01c080)
The buggy address belongs to the page:
page:ffffea0007280400 count:1 mapcount:0 mapping:ffff8801ca014080 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801ca014080 0000000000000000 0000000100000001
raw: ffffea00072b2c20 ffffea000732c820 ffff8801db002380 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ca016480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ca016500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ca016580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8801ca016600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ca016680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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