[PATCH 3.16 343/366] ipvs: fix buffer overflow with sync daemon and service

From: Ben Hutchings
Date: Sun Oct 14 2018 - 11:59:28 EST

3.16.60-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Julian Anastasov <ja@xxxxxx>

commit 52f96757905bbf0edef47f3ee6c7c784e7f8ff8a upstream.

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: e4ff67513096 ("ipvs: add sync_maxlen parameter for the sync daemon")
Fixes: 4da62fc70d7c ("[IPVS]: Fix for overflows")
Signed-off-by: Julian Anastasov <ja@xxxxxx>
Acked-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: Interface name is copied in start_sync_thread(),
not do_ip_vs_set_ctl()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2417,12 +2417,19 @@ do_ip_vs_set_ctl(struct sock *sk, int cm
}
}

+ 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;
}
@@ -2845,7 +2852,7 @@ static const struct nla_policy ip_vs_cmd
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 },
};

@@ -2858,7 +2865,7 @@ static const struct nla_policy ip_vs_svc
[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,
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -1738,8 +1738,9 @@ int start_sync_thread(struct net *net, i
if (ipvs->ms)
return -EEXIST;

- strlcpy(ipvs->master_mcast_ifn, mcast_ifn,
- sizeof(ipvs->master_mcast_ifn));
+ if (strscpy(ipvs->master_mcast_ifn, mcast_ifn,
+ sizeof(ipvs->master_mcast_ifn)) <= 0)
+ return -EINVAL;
ipvs->master_syncid = syncid;
name = "ipvs-m:%d:%d";
threadfn = sync_thread_master;
@@ -1747,8 +1748,9 @@ int start_sync_thread(struct net *net, i
if (ipvs->backup_threads)
return -EEXIST;

- strlcpy(ipvs->backup_mcast_ifn, mcast_ifn,
- sizeof(ipvs->backup_mcast_ifn));
+ if (strscpy(ipvs->backup_mcast_ifn, mcast_ifn,
+ sizeof(ipvs->backup_mcast_ifn)) <= 0)
+ return -EINVAL;
ipvs->backup_syncid = syncid;
name = "ipvs-b:%d:%d";
threadfn = sync_thread_backup;