Discussion:
KMSAN: uninit-value in ebt_stp_mt_check
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syzbot
2018-04-23 08:23:01 UTC
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Hello,

syzbot hit the following crash on
https://github.com/google/kmsan.git/master commit
a7f95e9c8a95e9fbb388c3999b61a17667cd3bbe (Sat Apr 21 13:50:22 2018 +0000)
kmsan: disable assembly checksums
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=5c06e318fc558cc27823

So far this crash happened 3 times on
https://github.com/google/kmsan.git/master.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5411555638247424
syzkaller reproducer:
https://syzkaller.appspot.com/x/repro.syz?id=6309829995921408
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=4546610964987904
Kernel config: https://syzkaller.appspot.com/x/.config?id=328654897048964367
compiler: clang version 7.0.0 (trunk 329391)

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Reported-by: syzbot+***@syzkaller.appspotmail.com
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==================================================================
BUG: KMSAN: uninit-value in ebt_stp_mt_check+0x248/0x410
net/bridge/netfilter/ebt_stp.c:164
CPU: 0 PID: 4520 Comm: syzkaller565841 Not tainted 4.16.0+ #85
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:683
ebt_stp_mt_check+0x248/0x410 net/bridge/netfilter/ebt_stp.c:164
xt_check_match+0x1449/0x1660 net/netfilter/x_tables.c:499
ebt_check_match net/bridge/netfilter/ebtables.c:374 [inline]
ebt_check_entry net/bridge/netfilter/ebtables.c:704 [inline]
translate_table+0x3ffd/0x5e10 net/bridge/netfilter/ebtables.c:945
do_replace_finish+0x1258/0x2ea0 net/bridge/netfilter/ebtables.c:1002
do_replace+0x707/0x770 net/bridge/netfilter/ebtables.c:1141
do_ebt_set_ctl+0x2ab/0x3c0 net/bridge/netfilter/ebtables.c:1518
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x476/0x4d0 net/netfilter/nf_sockopt.c:115
ip_setsockopt+0x24b/0x2b0 net/ipv4/ip_sockglue.c:1261
dccp_setsockopt+0x1c3/0x1f0 net/dccp/proto.c:576
sock_common_setsockopt+0x136/0x170 net/core/sock.c:2975
SYSC_setsockopt+0x4b8/0x570 net/socket.c:1849
SyS_setsockopt+0x76/0xa0 net/socket.c:1828
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x445d39
RSP: 002b:00007efff4e14da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 0000000000445d39
RDX: 0000000000000080 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000358 R09: 0000000000000000
R10: 00000000200008c0 R11: 0000000000000246 R12: 00000000006dac20
R13: 006567646972625f R14: 6f745f3168746576 R15: 0000000000000002

Local variable description: ----***@translate_table
Variable was created at:
translate_table+0xb9/0x5e10 net/bridge/netfilter/ebtables.c:833
do_replace_finish+0x1258/0x2ea0 net/bridge/netfilter/ebtables.c:1002
==================================================================


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