KMSAN: uninit-value in __udp4_lib_rcv

From: syzbot
Date: Thu Apr 19 2018 - 13:06:29 EST

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Hello,

syzbot hit the following crash on https://github.com/google/kmsan.git/master commit
35ff515e4bda2646f6c881d33951c306ea9c282a (Tue Apr 10 08:59:43 2018 +0000)
Merge pull request #11 from parkerduckworth/readme
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=493bccc5b8cfe9d5035e

So far this crash happened 11 times on https://github.com/google/kmsan.git/master.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=4935004320694272
syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=5133260011077632
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5329144879513600
Kernel config: https://syzkaller.appspot.com/x/.config?id=6627248707860932248
compiler: clang version 7.0.0 (trunk 329391)

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Reported-by: syzbot+493bccc5b8cfe9d5035e@xxxxxxxxxxxxxxxxxxxxxxxxx
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==================================================================
BUG: KMSAN: uninit-value in __udp4_lib_rcv+0x628/0x4740 net/ipv4/udp.c:2066
CPU: 1 PID: 3573 Comm: syzkaller192717 Not tainted 4.16.0+ #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x185/0x1d0 lib/dump_stack.c:53
kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
__msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
__udp4_lib_rcv+0x628/0x4740 net/ipv4/udp.c:2066
udp_rcv+0x5c/0x70 net/ipv4/udp.c:2287
ip_local_deliver_finish+0x6ed/0xd40 net/ipv4/ip_input.c:216
NF_HOOK include/linux/netfilter.h:288 [inline]
ip_local_deliver+0x43c/0x4e0 net/ipv4/ip_input.c:257
dst_input include/net/dst.h:449 [inline]
ip_rcv_finish+0x1253/0x16d0 net/ipv4/ip_input.c:397
NF_HOOK include/linux/netfilter.h:288 [inline]
ip_rcv+0x119d/0x16f0 net/ipv4/ip_input.c:493
__netif_receive_skb_core+0x47cf/0x4a80 net/core/dev.c:4562
__netif_receive_skb net/core/dev.c:4627 [inline]
process_backlog+0x62d/0xe20 net/core/dev.c:5307
napi_poll net/core/dev.c:5705 [inline]
net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
__do_softirq+0x56d/0x93d kernel/softirq.c:285
do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
</IRQ>
do_softirq kernel/softirq.c:329 [inline]
__local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
ip_finish_output2+0x124e/0x1380 net/ipv4/ip_output.c:231
ip_finish_output+0xcb0/0xff0 net/ipv4/ip_output.c:317
NF_HOOK_COND include/linux/netfilter.h:277 [inline]
ip_output+0x502/0x5c0 net/ipv4/ip_output.c:405
dst_output include/net/dst.h:443 [inline]
ip_local_out net/ipv4/ip_output.c:124 [inline]
ip_send_skb+0x5f3/0x820 net/ipv4/ip_output.c:1414
ip_push_pending_frames+0x105/0x170 net/ipv4/ip_output.c:1434
raw_sendmsg+0x2960/0x3ed0 net/ipv4/raw.c:684
inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:764
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
__sys_sendmsg net/socket.c:2080 [inline]
SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
SyS_sendmsg+0x54/0x80 net/socket.c:2087
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43fe99
RSP: 002b:00007ffca5bf5be8 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fe99
RDX: 0000000000000000 RSI: 00000000200002c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000217 R12: 00000000004017c0
R13: 0000000000401850 R14: 0000000000000000 R15: 0000000000000000

Uninit was stored to memory at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
kmsan_memcpy_origins+0x11d/0x170 mm/kmsan/kmsan.c:526
__msan_memcpy+0x19f/0x1f0 mm/kmsan/kmsan_instr.c:470
skb_copy_bits+0x63a/0xdb0 net/core/skbuff.c:2046
__pskb_pull_tail+0x483/0x22e0 net/core/skbuff.c:1883
pskb_may_pull include/linux/skbuff.h:2112 [inline]
__udp4_lib_rcv+0x55f/0x4740 net/ipv4/udp.c:2058
udp_rcv+0x5c/0x70 net/ipv4/udp.c:2287
ip_local_deliver_finish+0x6ed/0xd40 net/ipv4/ip_input.c:216
NF_HOOK include/linux/netfilter.h:288 [inline]
ip_local_deliver+0x43c/0x4e0 net/ipv4/ip_input.c:257
dst_input include/net/dst.h:449 [inline]
ip_rcv_finish+0x1253/0x16d0 net/ipv4/ip_input.c:397
NF_HOOK include/linux/netfilter.h:288 [inline]
ip_rcv+0x119d/0x16f0 net/ipv4/ip_input.c:493
__netif_receive_skb_core+0x47cf/0x4a80 net/core/dev.c:4562
__netif_receive_skb net/core/dev.c:4627 [inline]
process_backlog+0x62d/0xe20 net/core/dev.c:5307
napi_poll net/core/dev.c:5705 [inline]
net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
__do_softirq+0x56d/0x93d kernel/softirq.c:285
Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:814
kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:868
__alloc_pages_nodemask+0xf5b/0x5dc0 mm/page_alloc.c:4283
alloc_pages_current+0x6b5/0x970 mm/mempolicy.c:2055
alloc_pages include/linux/gfp.h:494 [inline]
skb_page_frag_refill+0x3ba/0x5e0 net/core/sock.c:2208
sk_page_frag_refill+0xa4/0x340 net/core/sock.c:2228
__ip_append_data+0x107e/0x3d10 net/ipv4/ip_output.c:1057
ip_append_data+0x2fb/0x440 net/ipv4/ip_output.c:1170
raw_sendmsg+0x287b/0x3ed0 net/ipv4/raw.c:678
inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:764
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
__sys_sendmsg net/socket.c:2080 [inline]
SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
SyS_sendmsg+0x54/0x80 net/socket.c:2087
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
==================================================================

---
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