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BUG: KMSAN: uninit-value in copyout lib/iov_iter.c:140 [inline]
BUG: KMSAN: uninit-value in _copy_to_iter+0x45f/0x2800 lib/iov_iter.c:571
CPU: 1 PID: 11087 Comm: syz-executor6 Not tainted 4.17.0-rc5+ #103
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+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x149/0x260 mm/kmsan/kmsan.c:1084
 kmsan_internal_check_memory+0x135/0x1e0 mm/kmsan/kmsan.c:1177
 kmsan_copy_to_user+0x75/0x160 mm/kmsan/kmsan.c:1219
 copyout lib/iov_iter.c:140 [inline]
 _copy_to_iter+0x45f/0x2800 lib/iov_iter.c:571
 copy_to_iter include/linux/uio.h:106 [inline]
 skb_copy_datagram_iter+0x443/0xf70 net/core/datagram.c:431
 skb_copy_datagram_msg include/linux/skbuff.h:3268 [inline]
 packet_recvmsg+0x75a/0x1d10 net/packet/af_packet.c:3350
 sock_recvmsg_nosec net/socket.c:802 [inline]
 sock_recvmsg net/socket.c:809 [inline]
 __sys_recvfrom+0x643/0x810 net/socket.c:1846
 __do_sys_recvfrom net/socket.c:1864 [inline]
 __se_sys_recvfrom net/socket.c:1860 [inline]
 __x64_sys_recvfrom+0x1a2/0x210 net/socket.c:1860
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x455a09
RSP: 002b:00007fb3cfa3dc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007fb3cfa3e6d4 RCX: 0000000000455a09
RDX: 0000000000000098 RSI: 0000000020000280 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000020000140 R09: 0000000000000080
R10: 0000000000000040 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000056c R14: 00000000006fd2c0 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:189
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:315
 kmsan_slab_alloc+0x10/0x20 mm/kmsan/kmsan.c:322
 slab_post_alloc_hook mm/slab.h:446 [inline]
 slab_alloc_node mm/slub.c:2753 [inline]
 __kmalloc_node_track_caller+0xb32/0x11b0 mm/slub.c:4395
 __kmalloc_reserve net/core/skbuff.c:138 [inline]
 __alloc_skb+0x2cb/0x9e0 net/core/skbuff.c:206
 alloc_skb include/linux/skbuff.h:988 [inline]
 alloc_skb_with_frags+0x1e6/0xb80 net/core/skbuff.c:5254
 sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2088
 packet_alloc_skb net/packet/af_packet.c:2810 [inline]
 packet_snd net/packet/af_packet.c:2901 [inline]
 packet_sendmsg+0x6584/0x8ab0 net/packet/af_packet.c:2976
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg net/socket.c:639 [inline]
 __sys_sendto+0x6c0/0x7e0 net/socket.c:1789
 __do_sys_sendto net/socket.c:1801 [inline]
 __se_sys_sendto net/socket.c:1797 [inline]
 __x64_sys_sendto+0x1a1/0x210 net/socket.c:1797
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 4-5 of 44 are uninitialized
Memory access starts at ffff880136fc1c64
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