KMSAN: uninit-value in netif_skb_features

From: syzbot
Date: Thu Apr 12 2018 - 04:01:12 EST

Hello,

syzbot hit the following crash on https://github.com/google/kmsan.git/master commit
e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +0000)
kmsan: temporarily disable visitAsmInstruction() to help syzbot
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=0bbe42c764feafa82c5a

So far this crash happened 30 times on https://github.com/google/kmsan.git/master.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=4850744041668608
syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=6289386287136768
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=4577411249209344
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+0bbe42c764feafa82c5a@xxxxxxxxxxxxxxxxxxxxxxxxx
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==================================================================
BUG: KMSAN: uninit-value in eth_type_vlan include/linux/if_vlan.h:283 [inline]
BUG: KMSAN: uninit-value in skb_vlan_tagged_multi include/linux/if_vlan.h:656 [inline]
BUG: KMSAN: uninit-value in vlan_features_check include/linux/if_vlan.h:672 [inline]
BUG: KMSAN: uninit-value in dflt_features_check net/core/dev.c:2949 [inline]
BUG: KMSAN: uninit-value in netif_skb_features+0xd1b/0xdc0 net/core/dev.c:3009
CPU: 1 PID: 3582 Comm: syzkaller435149 Not tainted 4.16.0+ #82
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+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
eth_type_vlan include/linux/if_vlan.h:283 [inline]
skb_vlan_tagged_multi include/linux/if_vlan.h:656 [inline]
vlan_features_check include/linux/if_vlan.h:672 [inline]
dflt_features_check net/core/dev.c:2949 [inline]
netif_skb_features+0xd1b/0xdc0 net/core/dev.c:3009
validate_xmit_skb+0x89/0x1320 net/core/dev.c:3084
__dev_queue_xmit+0x1cb2/0x2b60 net/core/dev.c:3549
dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
packet_snd net/packet/af_packet.c:2944 [inline]
packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
sock_write_iter+0x3b9/0x470 net/socket.c:909
do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
do_iter_write+0x30d/0xd40 fs/read_write.c:932
vfs_writev fs/read_write.c:977 [inline]
do_writev+0x3c9/0x830 fs/read_write.c:1012
SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
SyS_writev+0x56/0x80 fs/read_write.c:1082
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43ffa9
RSP: 002b:00007fff2cff3948 EFLAGS: 00000217 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ffa9
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004018d0
R13: 0000000000401960 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
slab_post_alloc_hook mm/slab.h:445 [inline]
slab_alloc_node mm/slub.c:2737 [inline]
__kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
__kmalloc_reserve net/core/skbuff.c:138 [inline]
__alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
alloc_skb include/linux/skbuff.h:984 [inline]
alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
sock_alloc_send_pskb+0xb56/0x1190 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+0x6444/0x8a10 net/packet/af_packet.c:2969
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
sock_write_iter+0x3b9/0x470 net/socket.c:909
do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
do_iter_write+0x30d/0xd40 fs/read_write.c:932
vfs_writev fs/read_write.c:977 [inline]
do_writev+0x3c9/0x830 fs/read_write.c:1012
SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
SyS_writev+0x56/0x80 fs/read_write.c:1082
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
==================================================================


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