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BUG: KASAN: use-after-free in tcp_highest_sack_seq include/net/tcp.h:1706 [inline]
BUG: KASAN: use-after-free in tcp_ack+0x42bb/0x4fd0 net/ipv4/tcp_input.c:3537
dccp_invalid_packet: P.Data Offset(0) too small
Read of size 4 at addr ffff8801d49c7a68 by task syz-executor2/8780

CPU: 0 PID: 8780 Comm: syz-executor2 Not tainted 4.14.0-rc8+ #123
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
dccp_invalid_packet: P.Data Offset(0) too small
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 tcp_highest_sack_seq include/net/tcp.h:1706 [inline]
 tcp_ack+0x42bb/0x4fd0 net/ipv4/tcp_input.c:3537
 tcp_rcv_established+0x672/0x18a0 net/ipv4/tcp_input.c:5439
 tcp_v4_do_rcv+0x2ab/0x7d0 net/ipv4/tcp_ipv4.c:1468
 sk_backlog_rcv include/net/sock.h:914 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2266
 release_sock+0xa4/0x2a0 net/core/sock.c:2781
 tcp_sendmsg+0x3a/0x50 net/ipv4/tcp.c:1462
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 SYSC_sendto+0x352/0x5a0 net/socket.c:1750
 SyS_sendto+0x40/0x50 net/socket.c:1718
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x452879
RSP: 002b:00007fd915ccebe8 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452879
RDX: 0000000000000002 RSI: 0000000020023ffe RDI: 0000000000000013
RBP: 0000000000000000 R08: 0000000020000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007fd915ccf9c0 R15: 0000000000000000

Allocated by task 8780:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc_node+0x144/0x760 mm/slab.c:3652
 __alloc_skb+0xf1/0x780 net/core/skbuff.c:194
 alloc_skb_fclone include/linux/skbuff.h:1026 [inline]
 sk_stream_alloc_skb+0x11d/0x900 net/ipv4/tcp.c:870
 tcp_sendmsg_locked+0x1341/0x3b80 net/ipv4/tcp.c:1299
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1461
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 SYSC_sendto+0x352/0x5a0 net/socket.c:1750
 SyS_sendto+0x40/0x50 net/socket.c:1718
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 8780:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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:3504 [inline]
 kmem_cache_free+0x77/0x280 mm/slab.c:3764
 kfree_skbmem+0xdd/0x1d0 net/core/skbuff.c:607
 __kfree_skb+0x1d/0x20 net/core/skbuff.c:646
 tcp_check_urg net/ipv4/tcp_input.c:5105 [inline]
 tcp_urg+0x9fe/0xbd0 net/ipv4/tcp_input.c:5123
 tcp_rcv_established+0x832/0x18a0 net/ipv4/tcp_input.c:5445
 tcp_v4_do_rcv+0x2ab/0x7d0 net/ipv4/tcp_ipv4.c:1468
 sk_backlog_rcv include/net/sock.h:914 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2266
 release_sock+0xa4/0x2a0 net/core/sock.c:2781
 tcp_sendmsg+0x3a/0x50 net/ipv4/tcp.c:1462
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 SYSC_sendto+0x352/0x5a0 net/socket.c:1750
 SyS_sendto+0x40/0x50 net/socket.c:1718
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801d49c7a40
 which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 40 bytes inside of
 456-byte region [ffff8801d49c7a40, ffff8801d49c7c08)
The buggy address belongs to the page:
page:ffffea00075271c0 count:1 mapcount:0 mapping:ffff8801d49c7040 index:0xffff8801d49c72c0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d49c7040 ffff8801d49c72c0 0000000100000005
raw: ffffea0007148820 ffffea000723b5a0 ffff8801d9827cc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d49c7900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d49c7980: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d49c7a00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801d49c7a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d49c7b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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