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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
Read of size 4 at addr ffff8801d0b5e568 by task syz-fuzzer/3041

CPU: 1 PID: 3041 Comm: syz-fuzzer Not tainted 4.14.0-next-20171113+ #41
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __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_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
 tcp_v4_rcv+0x24e5/0x2f80 net/ipv4/tcp_ipv4.c:1729
 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:250 [inline]
 ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:466 [inline]
 ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:250 [inline]
 ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1a3e/0x3450 net/core/dev.c:4478
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4543
 process_backlog+0x203/0x740 net/core/dev.c:5222
 napi_poll net/core/dev.c:5620 [inline]
 net_rx_action+0x792/0x1910 net/core/dev.c:5686
 __do_softirq+0x29d/0xbb2 kernel/softirq.c:285
 invoke_softirq kernel/softirq.c:365 [inline]
 irq_exit+0x1d3/0x210 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:540 [inline]
 smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:791
 </IRQ>
RIP: 0033:0x77517d
RSP: 002b:000000c425895770 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff11
RAX: 000000c4414ec720 RBX: 000000c427a09720 RCX: 0000000000f2cd40
RDX: 000000000087f797 RSI: 000000c427a09720 RDI: 0000000000000000
RBP: 000000c425895788 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000727790 R11: 00000000ffffffff R12: 000000c441e394a6
R13: 0000000000000001 R14: 00000000000000ff R15: 0000000000000000

Allocated by task 19327:
 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:3638
 __alloc_skb+0xf1/0x780 net/core/skbuff.c:193
 alloc_skb_fclone include/linux/skbuff.h:1023 [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:632 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:642
 SYSC_sendto+0x358/0x5a0 net/socket.c:1749
 SyS_sendto+0x40/0x50 net/socket.c:1717
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 19327:
 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:3492 [inline]
 kmem_cache_free+0x77/0x280 mm/slab.c:3750
 kfree_skbmem+0xdd/0x1d0 net/core/skbuff.c:603
 __kfree_skb+0x1d/0x20 net/core/skbuff.c:642
 tcp_collapse_one+0x114/0x1e0 net/ipv4/tcp_input.c:4685
 tcp_collapse+0x935/0xd20 net/ipv4/tcp_input.c:4799
 tcp_prune_queue net/ipv4/tcp_input.c:4915 [inline]
 tcp_try_rmem_schedule+0xaab/0x1820 net/ipv4/tcp_input.c:4352
 tcp_data_queue+0x7bd/0x3dd0 net/ipv4/tcp_input.c:4596
 tcp_rcv_established+0x844/0x18a0 net/ipv4/tcp_input.c:5448
 tcp_v4_do_rcv+0x2ab/0x7d0 net/ipv4/tcp_ipv4.c:1468
 sk_backlog_rcv include/net/sock.h:909 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2264
 release_sock+0xa4/0x2a0 net/core/sock.c:2778
 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:632 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:642
 ___sys_sendmsg+0x75b/0x8a0 net/socket.c:2048
 __sys_sendmsg+0xe5/0x210 net/socket.c:2082
 SYSC_sendmsg net/socket.c:2093 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2089
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d0b5e540
 which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 40 bytes inside of
 456-byte region [ffff8801d0b5e540, ffff8801d0b5e708)
The buggy address belongs to the page:
page:ffffea000742d780 count:1 mapcount:0 mapping:ffff8801d0b5e040 index:0xffff8801d0b5e7c0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d0b5e040 ffff8801d0b5e7c0 0000000100000005
raw: ffffea0007540660 ffffea0007155460 ffff8801d9d1c680 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d0b5e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d0b5e480: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d0b5e500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801d0b5e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d0b5e600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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