KMSAN: uninit-value in udp_tunnel6_xmit_skb

From: syzbot
Date: Wed Jan 29 2020 - 12:07:14 EST


Hello,

syzbot found the following crash on:

HEAD commit: 686a4f77 kmsan: don't compile memmove
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12696a4ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e10654781bc1f11c
dashboard link: https://syzkaller.appspot.com/bug?extid=0f342f32d39f96d04947
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0f342f32d39f96d04947@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in __arch_swab32 arch/x86/include/uapi/asm/swab.h:10 [inline]
BUG: KMSAN: uninit-value in __fswab32 include/uapi/linux/swab.h:59 [inline]
BUG: KMSAN: uninit-value in ip6_flow_hdr include/net/ipv6.h:942 [inline]
BUG: KMSAN: uninit-value in udp_tunnel6_xmit_skb+0xb74/0xec0 net/ipv6/ip6_udp_tunnel.c:107
CPU: 0 PID: 22812 Comm: syz-executor.3 Not tainted 5.5.0-rc5-syzkaller #0
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+0x1c9/0x220 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
__arch_swab32 arch/x86/include/uapi/asm/swab.h:10 [inline]
__fswab32 include/uapi/linux/swab.h:59 [inline]
ip6_flow_hdr include/net/ipv6.h:942 [inline]
udp_tunnel6_xmit_skb+0xb74/0xec0 net/ipv6/ip6_udp_tunnel.c:107
geneve6_xmit_skb drivers/net/geneve.c:973 [inline]
geneve_xmit+0x1d9a/0x2c20 drivers/net/geneve.c:1001
__netdev_start_xmit include/linux/netdevice.h:4447 [inline]
netdev_start_xmit include/linux/netdevice.h:4461 [inline]
xmit_one net/core/dev.c:3420 [inline]
dev_hard_start_xmit+0x531/0xab0 net/core/dev.c:3436
__dev_queue_xmit+0x37de/0x4220 net/core/dev.c:4013
dev_queue_xmit+0x4b/0x60 net/core/dev.c:4046
packet_snd net/packet/af_packet.c:2966 [inline]
packet_sendmsg+0x8436/0x92f0 net/packet/af_packet.c:2991
sock_sendmsg_nosec net/socket.c:639 [inline]
sock_sendmsg net/socket.c:659 [inline]
____sys_sendmsg+0x12b6/0x1350 net/socket.c:2330
___sys_sendmsg net/socket.c:2384 [inline]
__sys_sendmsg+0x451/0x5f0 net/socket.c:2417
__do_sys_sendmsg net/socket.c:2426 [inline]
__se_sys_sendmsg+0x97/0xb0 net/socket.c:2424
__x64_sys_sendmsg+0x4a/0x70 net/socket.c:2424
do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45b349
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd193e8ec78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd193e8f6d4 RCX: 000000000045b349
RDX: 0000000000000881 RSI: 0000000020007780 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009c0 R14: 00000000004cb2b4 R15: 000000000075bf2c

Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82
slab_alloc_node mm/slub.c:2774 [inline]
__kmalloc_node_track_caller+0xb40/0x1200 mm/slub.c:4382
__kmalloc_reserve net/core/skbuff.c:141 [inline]
__alloc_skb+0x2fd/0xac0 net/core/skbuff.c:209
alloc_skb include/linux/skbuff.h:1049 [inline]
alloc_skb_with_frags+0x18c/0xa70 net/core/skbuff.c:5664
sock_alloc_send_pskb+0xada/0xc60 net/core/sock.c:2242
packet_alloc_skb net/packet/af_packet.c:2814 [inline]
packet_snd net/packet/af_packet.c:2909 [inline]
packet_sendmsg+0x656e/0x92f0 net/packet/af_packet.c:2991
sock_sendmsg_nosec net/socket.c:639 [inline]
sock_sendmsg net/socket.c:659 [inline]
____sys_sendmsg+0x12b6/0x1350 net/socket.c:2330
___sys_sendmsg net/socket.c:2384 [inline]
__sys_sendmsg+0x451/0x5f0 net/socket.c:2417
__do_sys_sendmsg net/socket.c:2426 [inline]
__se_sys_sendmsg+0x97/0xb0 net/socket.c:2424
__x64_sys_sendmsg+0x4a/0x70 net/socket.c:2424
do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================


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