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BUG: KASAN: use-after-free in tcp_skb_pcount include/net/tcp.h:912 [inline]
BUG: KASAN: use-after-free in tcp_init_tso_segs+0x19d/0x1f0 net/ipv4/tcp_output.c:1790
Read of size 2 at addr ffff8881c6f27930 by task syz-executor.3/24198

CPU: 1 PID: 24198 Comm: syz-executor.3 Not tainted 4.14.143+ #0
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xca/0x134 lib/dump_stack.c:53
 print_address_description+0x60/0x226 mm/kasan/report.c:187
 __kasan_report.cold+0x1a/0x41 mm/kasan/report.c:316
 tcp_skb_pcount include/net/tcp.h:912 [inline]
 tcp_init_tso_segs+0x19d/0x1f0 net/ipv4/tcp_output.c:1790
 tcp_write_xmit+0x15a/0x4730 net/ipv4/tcp_output.c:2330
 __tcp_push_pending_frames+0xa0/0x230 net/ipv4/tcp_output.c:2563
 tcp_push+0x402/0x600 net/ipv4/tcp.c:715
 tcp_sendmsg_locked+0x21ed/0x2f50 net/ipv4/tcp.c:1426
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
 inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb7/0x100 net/socket.c:656
 sock_write_iter+0x20f/0x360 net/socket.c:925
 call_write_iter include/linux/fs.h:1788 [inline]
 new_sync_write fs/read_write.c:471 [inline]
 __vfs_write+0x401/0x5a0 fs/read_write.c:484
 vfs_write+0x17f/0x4d0 fs/read_write.c:546
 SYSC_write fs/read_write.c:594 [inline]
 SyS_write+0x102/0x250 fs/read_write.c:586
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4598e9
RSP: 002b:00007f341ea2dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004598e9
RDX: 00000001000001bd RSI: 0000000020002300 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f341ea2e6d4
R13: 00000000004c99fa R14: 00000000004e10d0 R15: 00000000ffffffff

Allocated by task 24198:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc.part.0+0x53/0xc0 mm/kasan/common.c:495
 slab_post_alloc_hook mm/slab.h:439 [inline]
 slab_alloc_node mm/slub.c:2792 [inline]
 slab_alloc mm/slub.c:2800 [inline]
 kmem_cache_alloc+0xee/0x360 mm/slub.c:2805
 kmem_cache_alloc_node include/linux/slab.h:361 [inline]
 __alloc_skb+0xea/0x5c0 net/core/skbuff.c:193
 alloc_skb_fclone include/linux/skbuff.h:1022 [inline]
 sk_stream_alloc_skb+0xf4/0x8a0 net/ipv4/tcp.c:855
 tcp_sendmsg_locked+0xf11/0x2f50 net/ipv4/tcp.c:1301
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
 inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb7/0x100 net/socket.c:656
 sock_write_iter+0x20f/0x360 net/socket.c:925
 call_write_iter include/linux/fs.h:1788 [inline]
 new_sync_write fs/read_write.c:471 [inline]
 __vfs_write+0x401/0x5a0 fs/read_write.c:484
 vfs_write+0x17f/0x4d0 fs/read_write.c:546
 SYSC_write fs/read_write.c:594 [inline]
 SyS_write+0x102/0x250 fs/read_write.c:586
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

Freed by task 24198:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x164/0x210 mm/kasan/common.c:457
 slab_free_hook mm/slub.c:1407 [inline]
 slab_free_freelist_hook mm/slub.c:1458 [inline]
 slab_free mm/slub.c:3039 [inline]
 kmem_cache_free+0xd7/0x3b0 mm/slub.c:3055
 kfree_skbmem+0x84/0x110 net/core/skbuff.c:607
 sk_wmem_free_skb include/net/sock.h:1416 [inline]
 tcp_remove_empty_skb net/ipv4/tcp.c:929 [inline]
 tcp_remove_empty_skb+0x264/0x320 net/ipv4/tcp.c:923
 tcp_sendmsg_locked+0x1c09/0x2f50 net/ipv4/tcp.c:1435
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
 inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb7/0x100 net/socket.c:656
 sock_write_iter+0x20f/0x360 net/socket.c:925
 call_write_iter include/linux/fs.h:1788 [inline]
 new_sync_write fs/read_write.c:471 [inline]
 __vfs_write+0x401/0x5a0 fs/read_write.c:484
 vfs_write+0x17f/0x4d0 fs/read_write.c:546
 SYSC_write fs/read_write.c:594 [inline]
 SyS_write+0x102/0x250 fs/read_write.c:586
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

The buggy address belongs to the object at ffff8881c6f27900
 which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 48 bytes inside of
 456-byte region [ffff8881c6f27900, ffff8881c6f27ac8)
The buggy address belongs to the page:
page:ffffea00071bc980 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 00000001800c000c
raw: 0000000000000000 0000000600000001 ffff8881dab70400 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c6f27800: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff8881c6f27880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881c6f27900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8881c6f27980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c6f27a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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