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Julian Anastasovbwhacks
Julian Anastasov
authored and
bwhacks
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ipvs: fix buffer overflow with sync daemon and service
commit 52f9675 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: [email protected] Fixes: e4ff675 ("ipvs: add sync_maxlen parameter for the sync daemon") Fixes: 4da62fc ("[IPVS]: Fix for overflows") Signed-off-by: Julian Anastasov <[email protected]> Acked-by: Simon Horman <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]> [bwh: Backported to 3.16: Interface name is copied in start_sync_thread(), not do_ip_vs_set_ctl()] Signed-off-by: Ben Hutchings <[email protected]>
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‎net/netfilter/ipvs/ip_vs_ctl.c‎

Lines changed: 11 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -2417,12 +2417,19 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
24172417
}
24182418
}
24192419

2420+
if ((cmd == IP_VS_SO_SET_ADD || cmd == IP_VS_SO_SET_EDIT) &&
2421+
strnlen(usvc.sched_name, IP_VS_SCHEDNAME_MAXLEN) ==
2422+
IP_VS_SCHEDNAME_MAXLEN) {
2423+
ret = -EINVAL;
2424+
goto out_unlock;
2425+
}
2426+
24202427
/* Check for valid protocol: TCP or UDP or SCTP, even for fwmark!=0 */
24212428
if (usvc.protocol != IPPROTO_TCP && usvc.protocol != IPPROTO_UDP &&
24222429
usvc.protocol != IPPROTO_SCTP) {
2423-
pr_err("set_ctl: invalid protocol: %d %pI4:%d %s\n",
2430+
pr_err("set_ctl: invalid protocol: %d %pI4:%d\n",
24242431
usvc.protocol, &usvc.addr.ip,
2425-
ntohs(usvc.port), usvc.sched_name);
2432+
ntohs(usvc.port));
24262433
ret = -EFAULT;
24272434
goto out_unlock;
24282435
}
@@ -2845,7 +2852,7 @@ static const struct nla_policy ip_vs_cmd_policy[IPVS_CMD_ATTR_MAX + 1] = {
28452852
static const struct nla_policy ip_vs_daemon_policy[IPVS_DAEMON_ATTR_MAX + 1] = {
28462853
[IPVS_DAEMON_ATTR_STATE] = { .type = NLA_U32 },
28472854
[IPVS_DAEMON_ATTR_MCAST_IFN] = { .type = NLA_NUL_STRING,
2848-
.len = IP_VS_IFNAME_MAXLEN },
2855+
.len = IP_VS_IFNAME_MAXLEN - 1 },
28492856
[IPVS_DAEMON_ATTR_SYNC_ID] = { .type = NLA_U32 },
28502857
};
28512858

@@ -2858,7 +2865,7 @@ static const struct nla_policy ip_vs_svc_policy[IPVS_SVC_ATTR_MAX + 1] = {
28582865
[IPVS_SVC_ATTR_PORT] = { .type = NLA_U16 },
28592866
[IPVS_SVC_ATTR_FWMARK] = { .type = NLA_U32 },
28602867
[IPVS_SVC_ATTR_SCHED_NAME] = { .type = NLA_NUL_STRING,
2861-
.len = IP_VS_SCHEDNAME_MAXLEN },
2868+
.len = IP_VS_SCHEDNAME_MAXLEN - 1 },
28622869
[IPVS_SVC_ATTR_PE_NAME] = { .type = NLA_NUL_STRING,
28632870
.len = IP_VS_PENAME_MAXLEN },
28642871
[IPVS_SVC_ATTR_FLAGS] = { .type = NLA_BINARY,

‎net/netfilter/ipvs/ip_vs_sync.c‎

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1738,17 +1738,19 @@ int start_sync_thread(struct net *net, int state, char *mcast_ifn, __u8 syncid)
17381738
if (ipvs->ms)
17391739
return -EEXIST;
17401740

1741-
strlcpy(ipvs->master_mcast_ifn, mcast_ifn,
1742-
sizeof(ipvs->master_mcast_ifn));
1741+
if (strscpy(ipvs->master_mcast_ifn, mcast_ifn,
1742+
sizeof(ipvs->master_mcast_ifn)) <= 0)
1743+
return -EINVAL;
17431744
ipvs->master_syncid = syncid;
17441745
name = "ipvs-m:%d:%d";
17451746
threadfn = sync_thread_master;
17461747
} else if (state == IP_VS_STATE_BACKUP) {
17471748
if (ipvs->backup_threads)
17481749
return -EEXIST;
17491750

1750-
strlcpy(ipvs->backup_mcast_ifn, mcast_ifn,
1751-
sizeof(ipvs->backup_mcast_ifn));
1751+
if (strscpy(ipvs->backup_mcast_ifn, mcast_ifn,
1752+
sizeof(ipvs->backup_mcast_ifn)) <= 0)
1753+
return -EINVAL;
17521754
ipvs->backup_syncid = syncid;
17531755
name = "ipvs-b:%d:%d";
17541756
threadfn = sync_thread_backup;

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