KASAN: stack-out-of-bounds Write in compat_copy_entries
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2018-04-25 05:19:02 UTC

syzbot hit the following crash on upstream commit
24cac7009cb1b211f1c793ecb6a462c03dc35818 (Tue Apr 24 21:16:40 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
syzbot dashboard link:

So far this crash happened 3 times on upstream.
syzkaller reproducer:
Raw console output:
Kernel config:
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
user-space arch: i386

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random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
IPVS: ftp: loaded support on port[0] = 21
BUG: KASAN: stack-out-of-bounds in strlcpy include/linux/string.h:300
BUG: KASAN: stack-out-of-bounds in compat_mtw_from_user
net/bridge/netfilter/ebtables.c:1957 [inline]
BUG: KASAN: stack-out-of-bounds in ebt_size_mwt
net/bridge/netfilter/ebtables.c:2059 [inline]
BUG: KASAN: stack-out-of-bounds in size_entry_mwt
net/bridge/netfilter/ebtables.c:2155 [inline]
BUG: KASAN: stack-out-of-bounds in compat_copy_entries+0x96c/0x14a0
Write of size 33 at addr ffff8801b0abf888 by task syz-executor0/4504

CPU: 0 PID: 4504 Comm: syz-executor0 Not tainted 4.17.0-rc2+ #40
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+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
memcpy+0x37/0x50 mm/kasan/kasan.c:303
strlcpy include/linux/string.h:300 [inline]
compat_mtw_from_user net/bridge/netfilter/ebtables.c:1957 [inline]
ebt_size_mwt net/bridge/netfilter/ebtables.c:2059 [inline]
size_entry_mwt net/bridge/netfilter/ebtables.c:2155 [inline]
compat_copy_entries+0x96c/0x14a0 net/bridge/netfilter/ebtables.c:2194
compat_do_replace+0x483/0x900 net/bridge/netfilter/ebtables.c:2285
compat_do_ebt_set_ctl+0x2ac/0x324 net/bridge/netfilter/ebtables.c:2367
compat_nf_sockopt net/netfilter/nf_sockopt.c:144 [inline]
compat_nf_setsockopt+0x9b/0x140 net/netfilter/nf_sockopt.c:156
compat_ip_setsockopt+0xff/0x140 net/ipv4/ip_sockglue.c:1279
inet_csk_compat_setsockopt+0x97/0x120 net/ipv4/inet_connection_sock.c:1041
compat_tcp_setsockopt+0x49/0x80 net/ipv4/tcp.c:2901
compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:3050
__compat_sys_setsockopt+0x1ab/0x7c0 net/compat.c:403
__do_compat_sys_setsockopt net/compat.c:416 [inline]
__se_compat_sys_setsockopt net/compat.c:413 [inline]
__ia32_compat_sys_setsockopt+0xbd/0x150 net/compat.c:413
do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline]
do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fb3cb9
RSP: 002b:00000000fff0c26c EFLAGS: 00000282 ORIG_RAX: 000000000000016e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000080 RSI: 0000000020000300 RDI: 00000000000005f4
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006c2afc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea0006c20101 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801b0abf780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801b0abf800: 00 00 00 00 00 f1 f1 f1 f1 00 00 f2 f2 f2 f2 f2
ffff8801b0abf880: f2 00 00 00 07 f3 f3 f3 f3 00 00 00 00 00 00 00
ffff8801b0abf900: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00
ffff8801b0abf980: 00 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00

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