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BUG: KASAN: use-after-free in copyout+0x7d/0xb0 lib/iov_iter.c:136
Read of size 1 at addr ffff8801bfb22080 by task syz-executor2/8918

CPU: 0 PID: 8918 Comm: syz-executor2 Not tainted 4.16.0-rc7+ #5
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+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
 copyout+0x7d/0xb0 lib/iov_iter.c:136
 _copy_to_iter+0x52b/0x13a0 lib/iov_iter.c:565
 copy_to_iter include/linux/uio.h:106 [inline]
 skb_copy_datagram_iter+0x1c2/0xac0 net/core/datagram.c:431
 skb_copy_datagram_msg include/linux/skbuff.h:3256 [inline]
 sock_recv_errqueue+0xbe/0x3e0 net/core/sock.c:2903
 packet_recvmsg+0xb2e/0x17a0 net/packet/af_packet.c:3296
 sock_recvmsg_nosec net/socket.c:803 [inline]
 sock_recvmsg+0xc9/0x110 net/socket.c:810
 ___sys_recvmsg+0x2a4/0x640 net/socket.c:2205
 __sys_recvmsg+0xe2/0x210 net/socket.c:2250
 SYSC_recvmsg net/socket.c:2262 [inline]
 SyS_recvmsg+0x2d/0x50 net/socket.c:2257
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4548b9
RSP: 002b:00007f3b2ed1fc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00007f3b2ed206d4 RCX: 00000000004548b9
RDX: 0000000000002000 RSI: 0000000020000580 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000495 R14: 00000000006f8e98 R15: 0000000000000000

Allocated by task 8918:
 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:552
 __do_kmalloc_node mm/slab.c:3670 [inline]
 __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3684
 __kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
 __alloc_skb+0x13b/0x780 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:983 [inline]
 alloc_skb_with_frags+0x10d/0x750 net/core/skbuff.c:5227
 sock_alloc_send_pskb+0x787/0x9b0 net/core/sock.c:2085
 packet_alloc_skb net/packet/af_packet.c:2803 [inline]
 packet_snd net/packet/af_packet.c:2894 [inline]
 packet_sendmsg+0x1ece/0x60b0 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 SYSC_sendto+0x361/0x5c0 net/socket.c:1747
 SyS_sendto+0x40/0x50 net/socket.c:1715
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 8918:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kfree+0xd9/0x260 mm/slab.c:3801
 skb_free_head+0x74/0xb0 net/core/skbuff.c:550
 skb_release_data+0x58c/0x790 net/core/skbuff.c:570
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 kfree_skb+0x15d/0x4c0 net/core/skbuff.c:659
 sit_tunnel_xmit+0x157/0x2d60 net/ipv6/sit.c:1042
 __netdev_start_xmit include/linux/netdevice.h:4066 [inline]
 netdev_start_xmit include/linux/netdevice.h:4075 [inline]
 xmit_one net/core/dev.c:3026 [inline]
 dev_hard_start_xmit+0x24e/0xac0 net/core/dev.c:3042
 __dev_queue_xmit+0x26bf/0x2fc0 net/core/dev.c:3557
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3590
 packet_snd net/packet/af_packet.c:2944 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 SYSC_sendto+0x361/0x5c0 net/socket.c:1747
 SyS_sendto+0x40/0x50 net/socket.c:1715
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801bfb22000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 128 bytes inside of
 512-byte region [ffff8801bfb22000, ffff8801bfb22200)
The buggy address belongs to the page:
page:ffffea0006fec880 count:1 mapcount:0 mapping:ffff8801bfb22000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bfb22000 0000000000000000 0000000100000006
raw: ffffea000733c9a0 ffffea0006f160e0 ffff8801dac00940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bfb21f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bfb22000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801bfb22080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801bfb22100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bfb22180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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