==================================================================
BUG: KASAN: use-after-free in tcp_connect+0x26c2/0x30b0 net/ipv4/tcp_output.c:3417
Read of size 4 at addr ffff8801c89d56a8 by task syz-executor.4/5839

CPU: 0 PID: 5839 Comm: syz-executor.4 Not tainted 4.9.168+ #39
 ffff8801c6e77998 ffffffff81b4f5d1 0000000000000000 ffffea0007227500
 ffff8801c89d56a8 0000000000000004 ffffffff8251f212 ffff8801c6e779d0
 ffffffff81506898 0000000000000000 ffff8801c89d56a8 ffff8801c89d56a8
Call Trace:
 [<00000000b58cbaf1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000b58cbaf1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<00000000eb77b0fe>] print_address_description+0x6f/0x23a mm/kasan/report.c:256
 [<00000000ce7a83b1>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<00000000ce7a83b1>] kasan_report mm/kasan/report.c:412 [inline]
 [<00000000ce7a83b1>] kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:397
 [<00000000ca5022ea>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 [<0000000059fc1d19>] tcp_connect+0x26c2/0x30b0 net/ipv4/tcp_output.c:3417
 [<0000000009668526>] tcp_v4_connect+0x1489/0x1c30 net/ipv4/tcp_ipv4.c:250
 [<0000000087993cb0>] __inet_stream_connect+0x706/0xbf0 net/ipv4/af_inet.c:623
 [<00000000ee3c2334>] inet_stream_connect+0x55/0xa0 net/ipv4/af_inet.c:687
 [<0000000083675fc8>] SYSC_connect net/socket.c:1576 [inline]
 [<0000000083675fc8>] SyS_connect+0x1a5/0x2e0 net/socket.c:1557
 [<00000000bd6ea880>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<00000000e15d226d>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 5837:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack mm/kasan/kasan.c:505 [inline]
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:609
 kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:594
 kasan_slab_alloc+0xf/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+0xd5/0x2b0 mm/slub.c:2728
 kmem_cache_alloc_node include/linux/slab.h:364 [inline]
 __alloc_skb+0xe7/0x5e0 net/core/skbuff.c:219
 alloc_skb_fclone include/linux/skbuff.h:966 [inline]
 sk_stream_alloc_skb+0xa3/0x5d0 net/ipv4/tcp.c:828
 tcp_sendmsg+0xe8d/0x2f90 net/ipv4/tcp.c:1230
 inet_sendmsg+0x202/0x4d0 net/ipv4/af_inet.c:766
 sock_sendmsg_nosec net/socket.c:649 [inline]
 sock_sendmsg+0xbe/0x110 net/socket.c:659
 SYSC_sendto net/socket.c:1684 [inline]
 SyS_sendto+0x201/0x340 net/socket.c:1652
 do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 5839:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack mm/kasan/kasan.c:505 [inline]
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0xb0/0x190 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+0xbe/0x310 mm/slub.c:2980
 kfree_skbmem+0x82/0x100 net/core/skbuff.c:648
 __kfree_skb+0x1e/0x30 net/core/skbuff.c:689
 sk_wmem_free_skb include/net/sock.h:1368 [inline]
 tcp_write_queue_purge include/net/tcp.h:1530 [inline]
 tcp_connect_init net/ipv4/tcp_output.c:3257 [inline]
 tcp_connect+0xa9b/0x30b0 net/ipv4/tcp_output.c:3388
 tcp_v4_connect+0x1489/0x1c30 net/ipv4/tcp_ipv4.c:250
 __inet_stream_connect+0x706/0xbf0 net/ipv4/af_inet.c:623
 inet_stream_connect+0x55/0xa0 net/ipv4/af_inet.c:687
 SYSC_connect net/socket.c:1576 [inline]
 SyS_connect+0x1a5/0x2e0 net/socket.c:1557
 do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the object at ffff8801c89d5680
 which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 40 bytes inside of
 456-byte region [ffff8801c89d5680, ffff8801c89d5848)
The buggy address belongs to the page:
page:ffffea0007227500 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c89d5580: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff8801c89d5600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c89d5680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801c89d5700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c89d5780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================