ipvs: fix buffer overflow with sync daemon and service

syzkaller reports for buffer overflow for interface name
when starting sync daemons [1]

What we do is that we copy user structure into larger stack
buffer but later we search NUL past the stack buffer.
The same happens for sched_name when adding/editing virtual server.

We are restricted by IP_VS_SCHEDNAME_MAXLEN and IP_VS_IFNAME_MAXLEN
being used as size in include/uapi/linux/ip_vs.h, so they
include the space for NUL.

As using strlcpy is wrong for unsafe source, replace it with
strscpy and add checks to return EINVAL if source string is not
NUL-terminated. The incomplete strlcpy fix comes from 2.6.13.

For the netlink interface reduce the len parameter for
IPVS_DAEMON_ATTR_MCAST_IFN and IPVS_SVC_ATTR_SCHED_NAME,
so that we get proper EINVAL.

[1]
kernel BUG at lib/string.c:1052!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 373 Comm: syz-executor936 Not tainted 4.17.0-rc4+ #45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:fortify_panic+0x13/0x20 lib/string.c:1051
RSP: 0018:ffff8801c976f800 EFLAGS: 00010282
RAX: 0000000000000022 RBX: 0000000000000040 RCX: 0000000000000000
RDX: 0000000000000022 RSI: ffffffff8160f6f1 RDI: ffffed00392edef6
RBP: ffff8801c976f800 R08: ffff8801cf4c62c0 R09: ffffed003b5e4fb0
R10: ffffed003b5e4fb0 R11: ffff8801daf27d87 R12: ffff8801c976fa20
R13: ffff8801c976fae4 R14: ffff8801c976fae0 R15: 000000000000048b
FS:  00007fd99f75e700(0000) GS:ffff8801daf00000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200001c0 CR3: 00000001d6843000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  strlen include/linux/string.h:270 [inline]
  strlcpy include/linux/string.h:293 [inline]
  do_ip_vs_set_ctl+0x31c/0x1d00 net/netfilter/ipvs/ip_vs_ctl.c:2388
  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
  nf_setsockopt+0x7d/0xd0 net/netfilter/nf_sockopt.c:115
  ip_setsockopt+0xd8/0xf0 net/ipv4/ip_sockglue.c:1253
  udp_setsockopt+0x62/0xa0 net/ipv4/udp.c:2487
  ipv6_setsockopt+0x149/0x170 net/ipv6/ipv6_sockglue.c:917
  tcp_setsockopt+0x93/0xe0 net/ipv4/tcp.c:3057
  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3046
  __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
  __do_sys_setsockopt net/socket.c:1914 [inline]
  __se_sys_setsockopt net/socket.c:1911 [inline]
  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447369
RSP: 002b:00007fd99f75dda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006e39e4 RCX: 0000000000447369
RDX: 000000000000048b RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000018 R09: 0000000000000000
R10: 00000000200001c0 R11: 0000000000000246 R12: 00000000006e39e0
R13: 75a1ff93f0896195 R14: 6f745f3168746576 R15: 0000000000000001
Code: 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b 48 89 df e8 d2 8f 48 fa eb
de 55 48 89 fe 48 c7 c7 60 65 64 88 48 89 e5 e8 91 dd f3 f9 <0f> 0b 90 90
90 90 90 90 90 90 90 90 90 55 48 89 e5 41 57 41 56
RIP: fortify_panic+0x13/0x20 lib/string.c:1051 RSP: ffff8801c976f800

Reported-and-tested-by: syzbot+aac887f77319868646df@syzkaller.appspotmail.com
Fixes: e4ff6751 ("ipvs: add sync_maxlen parameter for the sync daemon")
Fixes: 4da62fc7 ("[IPVS]: Fix for overflows")
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/ipvs/ip_vs_ctl.c

@@ -2381,8 +2381,10 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 			struct ipvs_sync_daemon_cfg cfg;
 
 			memset(&cfg, 0, sizeof(cfg));
-			strlcpy(cfg.mcast_ifn, dm->mcast_ifn,
-				sizeof(cfg.mcast_ifn));
+			ret = -EINVAL;
+			if (strscpy(cfg.mcast_ifn, dm->mcast_ifn,
+				    sizeof(cfg.mcast_ifn)) <= 0)
+				goto out_dec;
 			cfg.syncid = dm->syncid;
 			ret = start_sync_thread(ipvs, &cfg, dm->state);
 		} else {
@@ -2420,12 +2422,19 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 		}
 	}
 
+	if ((cmd == IP_VS_SO_SET_ADD || cmd == IP_VS_SO_SET_EDIT) &&
+	    strnlen(usvc.sched_name, IP_VS_SCHEDNAME_MAXLEN) ==
+	    IP_VS_SCHEDNAME_MAXLEN) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
 	/* Check for valid protocol: TCP or UDP or SCTP, even for fwmark!=0 */
 	if (usvc.protocol != IPPROTO_TCP && usvc.protocol != IPPROTO_UDP &&
 	    usvc.protocol != IPPROTO_SCTP) {
-		pr_err("set_ctl: invalid protocol: %d %pI4:%d %s\n",
+		pr_err("set_ctl: invalid protocol: %d %pI4:%d\n",
 		       usvc.protocol, &usvc.addr.ip,
-		       ntohs(usvc.port), usvc.sched_name);
+		       ntohs(usvc.port));
 		ret = -EFAULT;
 		goto out_unlock;
 	}
@@ -2847,7 +2856,7 @@ static const struct nla_policy ip_vs_cmd_policy[IPVS_CMD_ATTR_MAX + 1] = {
 static const struct nla_policy ip_vs_daemon_policy[IPVS_DAEMON_ATTR_MAX + 1] = {
 	[IPVS_DAEMON_ATTR_STATE]	= { .type = NLA_U32 },
 	[IPVS_DAEMON_ATTR_MCAST_IFN]	= { .type = NLA_NUL_STRING,
-					    .len = IP_VS_IFNAME_MAXLEN },
+					    .len = IP_VS_IFNAME_MAXLEN - 1 },
 	[IPVS_DAEMON_ATTR_SYNC_ID]	= { .type = NLA_U32 },
 	[IPVS_DAEMON_ATTR_SYNC_MAXLEN]	= { .type = NLA_U16 },
 	[IPVS_DAEMON_ATTR_MCAST_GROUP]	= { .type = NLA_U32 },
@@ -2865,7 +2874,7 @@ static const struct nla_policy ip_vs_svc_policy[IPVS_SVC_ATTR_MAX + 1] = {
 	[IPVS_SVC_ATTR_PORT]		= { .type = NLA_U16 },
 	[IPVS_SVC_ATTR_FWMARK]		= { .type = NLA_U32 },
 	[IPVS_SVC_ATTR_SCHED_NAME]	= { .type = NLA_NUL_STRING,
-					    .len = IP_VS_SCHEDNAME_MAXLEN },
+					    .len = IP_VS_SCHEDNAME_MAXLEN - 1 },
 	[IPVS_SVC_ATTR_PE_NAME]		= { .type = NLA_NUL_STRING,
 					    .len = IP_VS_PENAME_MAXLEN },
 	[IPVS_SVC_ATTR_FLAGS]		= { .type = NLA_BINARY,