==================================================================
BUG: KASAN: slab-out-of-bounds in skb_gro_receive+0xf5f/0x10e0 net/core/skbuff.c:3858
Read of size 16 at addr ffff88808c687ff0 by task syz-executor256/8028

CPU: 1 PID: 8028 Comm: syz-executor256 Not tainted 5.1.0-rc7-next-20190501 #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
 __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 __asan_report_load16_noabort+0x14/0x20 mm/kasan/generic_report.c:133
 skb_gro_receive+0xf5f/0x10e0 net/core/skbuff.c:3858
 udp_gro_receive_segment net/ipv4/udp_offload.c:384 [inline]
 call_gro_receive include/linux/netdevice.h:2328 [inline]
 udp_gro_receive+0xc63/0x1080 net/ipv4/udp_offload.c:415
 udp4_gro_receive+0x763/0xeb0 net/ipv4/udp_offload.c:479
 inet_gro_receive+0xe72/0x1110 net/ipv4/af_inet.c:1511
 dev_gro_receive+0x1cd0/0x23c0 net/core/dev.c:5584
 napi_gro_frags+0x36b/0xd10 net/core/dev.c:5846
 tun_get_user+0x2f3f/0x3ff0 drivers/net/tun.c:1981
 tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2027
 call_write_iter include/linux/fs.h:1866 [inline]
 do_iter_readv_writev+0x5e1/0x8e0 fs/read_write.c:681
 do_iter_write fs/read_write.c:957 [inline]
 do_iter_write+0x184/0x610 fs/read_write.c:938
 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1002
 do_writev+0x15e/0x370 fs/read_write.c:1037
 __do_sys_writev fs/read_write.c:1110 [inline]
 __se_sys_writev fs/read_write.c:1107 [inline]
 __x64_sys_writev+0x75/0xb0 fs/read_write.c:1107
 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441cc0
Code: 05 48 3d 01 f0 ff ff 0f 83 9d 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 83 3d 51 93 29 00 00 75 14 b8 14 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 74 09 fc ff c3 48 83 ec 08 e8 ba 2b 00 00
RSP: 002b:00007ffffce90e28 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007ffffce90e60 RCX: 0000000000441cc0
RDX: 0000000000000001 RSI: 00007ffffce90e80 RDI: 00000000000000f0
RBP: 0000000000000000 R08: 000000000000ffff R09: 0000555555780668
R10: 0000000020000040 R11: 0000000000000246 R12: 000000000000cb46
R13: 0000000000402b50 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7976:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_kmalloc mm/kasan/common.c:489 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:497
 slab_post_alloc_hook mm/slab.h:437 [inline]
 slab_alloc_node mm/slab.c:3299 [inline]
 kmem_cache_alloc_node+0x131/0x710 mm/slab.c:3609
 alloc_task_struct_node kernel/fork.c:160 [inline]
 dup_task_struct kernel/fork.c:848 [inline]
 copy_process.part.0+0x4426/0x67e0 kernel/fork.c:1872
 copy_process kernel/fork.c:1804 [inline]
 _do_fork+0x25d/0xfe0 kernel/fork.c:2372
 __do_sys_clone kernel/fork.c:2479 [inline]
 __se_sys_clone kernel/fork.c:2473 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2473
 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
 __cache_free mm/slab.c:3462 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3728
 free_task_struct kernel/fork.c:165 [inline]
 free_task+0xdd/0x120 kernel/fork.c:460
 __put_task_struct+0x1fd/0x4e0 kernel/fork.c:733
 put_task_struct include/linux/sched/task.h:99 [inline]
 delayed_put_task_struct+0x1ec/0x340 kernel/exit.c:181
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2092 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2310 [inline]
 rcu_core+0xbac/0x1510 kernel/rcu/tree.c:2291
 __do_softirq+0x266/0x95a kernel/softirq.c:293

The buggy address belongs to the object at ffff88808c6864c0
 which belongs to the cache task_struct of size 6080
The buggy address is located 880 bytes to the right of
 6080-byte region [ffff88808c6864c0, ffff88808c687c80)
The buggy address belongs to the page:
page:ffffea000231a180 count:1 mapcount:0 mapping:ffff88821bc427c0 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002326508 ffffea0002a10d88 ffff88821bc427c0
raw: 0000000000000000 ffff88808c6864c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808c687e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808c687f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808c687f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                             ^
 ffff88808c688000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88808c688080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================