[PATCH v4.19.y 1/2] netfilter: nfnetlink_cttimeout: pass default timeout policy to obj_to_nlattr

[PATCH v4.19.y 1/2] netfilter: nfnetlink_cttimeout: pass default timeout policy to obj_to_nlattr

[Zubin Mithra]

From: Pablo Neira Ayuso <pablo@netfilter.org>

commit 8866df9264a34e675b4ee8a151db819b87cce2d3 upstream

Otherwise, we hit a NULL pointer deference since handlers always assume
default timeout policy is passed.

  netlink: 24 bytes leftover after parsing attributes in process `syz-executor2'.
  kasan: CONFIG_KASAN_INLINE enabled
  kasan: GPF could be caused by NULL-ptr deref or user memory access
  general protection fault: 0000 [#1] PREEMPT SMP KASAN
  CPU: 0 PID: 9575 Comm: syz-executor1 Not tainted 4.19.0+ #312
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:icmp_timeout_obj_to_nlattr+0x77/0x170 net/netfilter/nf_conntrack_proto_icmp.c:297

Fixes: c779e849608a ("netfilter: conntrack: remove get_timeout() indirection")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
---
Notes:
* Syzkaller reported a general protection fault in icmp_timeout_obj_to_nlattri
when fuzzing a 4.19 kernel.
Call Trace:
 cttimeout_default_fill_info net/netfilter/nfnetlink_cttimeout.c:424 [inline]
 cttimeout_default_get+0x574/0x766 net/netfilter/nfnetlink_cttimeout.c:471
 nfnetlink_rcv_msg+0x544/0x5bd net/netfilter/nfnetlink.c:228
 netlink_rcv_skb+0x1cf/0x2a1 net/netlink/af_netlink.c:2454
 nfnetlink_rcv+0x30f/0x34a net/netfilter/nfnetlink.c:560
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x3c5/0x4c3 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0x829/0x88e net/netlink/af_netlink.c:1908
 sock_sendmsg_nosec+0x8c/0xad net/socket.c:621
 sock_sendmsg+0x4f/0x60 net/socket.c:631
 ___sys_sendmsg+0x4d6/0x63f net/socket.c:2116
 __sys_sendmsg+0xee/0x17b net/socket.c:2154
 do_syscall_64+0xf8/0x133 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

* This patch resolves the following conflicts when applying to 4.19:
- l3num is not used as an argument for cttimeout_default_fill_info() in 4.19
- nf_icmp_pernet, nf_tcp_pernet, nf_udp_pernet, nf_dccp_pernet,
nf_icmpv6_pernet, nf_sctp_pernet, nf_generic_pernet do not exist in
4.19. Expand the usage of those functions into one-liners.

* Tests run: Chrome OS tryjobs, Syzkaller reproducer

 net/netfilter/nfnetlink_cttimeout.c | 46 +++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
index a30f8ba4b89a..1dc4ea327cbe 100644
--- a/net/netfilter/nfnetlink_cttimeout.c
+++ b/net/netfilter/nfnetlink_cttimeout.c
@@ -392,7 +392,8 @@ static int cttimeout_default_set(struct net *net, struct sock *ctnl,
 static int
 cttimeout_default_fill_info(struct net *net, struct sk_buff *skb, u32 portid,
 			    u32 seq, u32 type, int event,
-			    const struct nf_conntrack_l4proto *l4proto)
+			    const struct nf_conntrack_l4proto *l4proto,
+			    const unsigned int *timeouts)
 {
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
@@ -421,7 +422,7 @@ cttimeout_default_fill_info(struct net *net, struct sk_buff *skb, u32 portid,
 		if (!nest_parms)
 			goto nla_put_failure;
 
-		ret = l4proto->ctnl_timeout.obj_to_nlattr(skb, NULL);
+		ret = l4proto->ctnl_timeout.obj_to_nlattr(skb, timeouts);
 		if (ret < 0)
 			goto nla_put_failure;
 
@@ -444,6 +445,7 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 				 struct netlink_ext_ack *extack)
 {
 	const struct nf_conntrack_l4proto *l4proto;
+	unsigned int *timeouts = NULL;
 	struct sk_buff *skb2;
 	int ret, err;
 	__u16 l3num;
@@ -456,12 +458,44 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 	l4num = nla_get_u8(cda[CTA_TIMEOUT_L4PROTO]);
 	l4proto = nf_ct_l4proto_find_get(l3num, l4num);
 
-	/* This protocol is not supported, skip. */
-	if (l4proto->l4proto != l4num) {
-		err = -EOPNOTSUPP;
+	err = -EOPNOTSUPP;
+	if (l4proto->l4proto != l4num)
 		goto err;
+
+	switch (l4proto->l4proto) {
+	case IPPROTO_ICMP:
+		timeouts = &net->ct.nf_ct_proto.icmp.timeout;
+		break;
+	case IPPROTO_TCP:
+		timeouts = net->ct.nf_ct_proto.tcp.timeouts;
+		break;
+	case IPPROTO_UDP:
+		timeouts = net->ct.nf_ct_proto.udp.timeouts;
+		break;
+	case IPPROTO_DCCP:
+#ifdef CONFIG_NF_CT_PROTO_DCCP
+		timeouts = net->ct.nf_ct_proto.dccp.dccp_timeout;
+#endif
+		break;
+	case IPPROTO_ICMPV6:
+		timeouts = &net->ct.nf_ct_proto.icmpv6.timeout;
+		break;
+	case IPPROTO_SCTP:
+#ifdef CONFIG_NF_CT_PROTO_SCTP
+		timeouts = net->ct.nf_ct_proto.sctp.timeouts;
+#endif
+		break;
+	case 255:
+		timeouts = &net->ct.nf_ct_proto.generic.timeout;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
 	}
 
+	if (!timeouts)
+		goto err;
+
 	skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (skb2 == NULL) {
 		err = -ENOMEM;
@@ -472,7 +506,7 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 					  nlh->nlmsg_seq,
 					  NFNL_MSG_TYPE(nlh->nlmsg_type),
 					  IPCTNL_MSG_TIMEOUT_DEFAULT_SET,
-					  l4proto);
+					  l4proto, timeouts);
 	if (ret <= 0) {
 		kfree_skb(skb2);
 		err = -ENOMEM;
-- 
2.21.0.392.gf8f6787159e-goog

[PATCH v4.19.y 2/2] netfilter: nfnetlink_cttimeout: fetch timeouts for udplite and gre, too

[Zubin Mithra]

From: Florian Westphal <fw@strlen.de>

commit 89259088c1b7fecb43e8e245dc931909132a4e03 upstream

syzbot was able to trigger the WARN in cttimeout_default_get() by
passing UDPLITE as l4protocol.  Alias UDPLITE to UDP, both use
same timeout values.

Furthermore, also fetch GRE timeouts.  GRE is a bit more complicated,
as it still can be a module and its netns_proto_gre struct layout isn't
visible outside of the gre module. Can't move timeouts around, it
appears conntrack sysctl unregister assumes net_generic() returns
nf_proto_net, so we get crash. Expose layout of netns_proto_gre instead.

A followup nf-next patch could make gre tracker be built-in as well
if needed, its not that large.

Last, make the WARN() mention the missing protocol value in case
anything else is missing.

Reported-by: syzbot+2fae8fa157dd92618cae@syzkaller.appspotmail.com
Fixes: 8866df9264a3 ("netfilter: nfnetlink_cttimeout: pass default timeout policy to obj_to_nlattr")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
---
 include/linux/netfilter/nf_conntrack_proto_gre.h | 13 +++++++++++++
 net/netfilter/nf_conntrack_proto_gre.c           | 14 ++------------
 net/netfilter/nfnetlink_cttimeout.c              | 15 +++++++++++++--
 3 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/include/linux/netfilter/nf_conntrack_proto_gre.h b/include/linux/netfilter/nf_conntrack_proto_gre.h
index b8d95564bd53..14edb795ab43 100644
--- a/include/linux/netfilter/nf_conntrack_proto_gre.h
+++ b/include/linux/netfilter/nf_conntrack_proto_gre.h
@@ -21,6 +21,19 @@ struct nf_ct_gre_keymap {
 	struct nf_conntrack_tuple tuple;
 };
 
+enum grep_conntrack {
+	GRE_CT_UNREPLIED,
+	GRE_CT_REPLIED,
+	GRE_CT_MAX
+};
+
+struct netns_proto_gre {
+	struct nf_proto_net	nf;
+	rwlock_t		keymap_lock;
+	struct list_head	keymap_list;
+	unsigned int		gre_timeouts[GRE_CT_MAX];
+};
+
 /* add new tuple->key_reply pair to keymap */
 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 			 struct nf_conntrack_tuple *t);
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index 650eb4fba2c5..841c472aae1c 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -43,24 +43,12 @@
 #include <linux/netfilter/nf_conntrack_proto_gre.h>
 #include <linux/netfilter/nf_conntrack_pptp.h>
 
-enum grep_conntrack {
-	GRE_CT_UNREPLIED,
-	GRE_CT_REPLIED,
-	GRE_CT_MAX
-};
-
 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
 	[GRE_CT_UNREPLIED]	= 30*HZ,
 	[GRE_CT_REPLIED]	= 180*HZ,
 };
 
 static unsigned int proto_gre_net_id __read_mostly;
-struct netns_proto_gre {
-	struct nf_proto_net	nf;
-	rwlock_t		keymap_lock;
-	struct list_head	keymap_list;
-	unsigned int		gre_timeouts[GRE_CT_MAX];
-};
 
 static inline struct netns_proto_gre *gre_pernet(struct net *net)
 {
@@ -408,6 +396,8 @@ static int __init nf_ct_proto_gre_init(void)
 {
 	int ret;
 
+	BUILD_BUG_ON(offsetof(struct netns_proto_gre, nf) != 0);
+
 	ret = register_pernet_subsys(&proto_gre_net_ops);
 	if (ret < 0)
 		goto out_pernet;
diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
index 1dc4ea327cbe..70a7382b9787 100644
--- a/net/netfilter/nfnetlink_cttimeout.c
+++ b/net/netfilter/nfnetlink_cttimeout.c
@@ -469,7 +469,8 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 	case IPPROTO_TCP:
 		timeouts = net->ct.nf_ct_proto.tcp.timeouts;
 		break;
-	case IPPROTO_UDP:
+	case IPPROTO_UDP: /* fallthrough */
+	case IPPROTO_UDPLITE:
 		timeouts = net->ct.nf_ct_proto.udp.timeouts;
 		break;
 	case IPPROTO_DCCP:
@@ -483,13 +484,23 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 	case IPPROTO_SCTP:
 #ifdef CONFIG_NF_CT_PROTO_SCTP
 		timeouts = net->ct.nf_ct_proto.sctp.timeouts;
+#endif
+		break;
+	case IPPROTO_GRE:
+#ifdef CONFIG_NF_CT_PROTO_GRE
+		if (l4proto->net_id) {
+			struct netns_proto_gre *net_gre;
+
+			net_gre = net_generic(net, *l4proto->net_id);
+			timeouts = net_gre->gre_timeouts;
+		}
 #endif
 		break;
 	case 255:
 		timeouts = &net->ct.nf_ct_proto.generic.timeout;
 		break;
 	default:
-		WARN_ON_ONCE(1);
+		WARN_ONCE(1, "Missing timeouts for proto %d", l4proto->l4proto);
 		break;
 	}
 
-- 
2.21.0.392.gf8f6787159e-goog

Re: [PATCH v4.19.y 1/2] netfilter: nfnetlink_cttimeout: pass default timeout policy to obj_to_nlattr

[Sasha Levin]

On Fri, Apr 12, 2019 at 10:55:02AM -0700, Zubin Mithra wrote:
>From: Pablo Neira Ayuso <pablo@netfilter.org>
>
>commit 8866df9264a34e675b4ee8a151db819b87cce2d3 upstream
>
>Otherwise, we hit a NULL pointer deference since handlers always assume
>default timeout policy is passed.
>
>  netlink: 24 bytes leftover after parsing attributes in process `syz-executor2'.
>  kasan: CONFIG_KASAN_INLINE enabled
>  kasan: GPF could be caused by NULL-ptr deref or user memory access
>  general protection fault: 0000 [#1] PREEMPT SMP KASAN
>  CPU: 0 PID: 9575 Comm: syz-executor1 Not tainted 4.19.0+ #312
>  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>  RIP: 0010:icmp_timeout_obj_to_nlattr+0x77/0x170 net/netfilter/nf_conntrack_proto_icmp.c:297
>
>Fixes: c779e849608a ("netfilter: conntrack: remove get_timeout() indirection")
>Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
>Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
>Signed-off-by: Zubin Mithra <zsm@chromium.org>
>---
>Notes:
>* Syzkaller reported a general protection fault in icmp_timeout_obj_to_nlattri
>when fuzzing a 4.19 kernel.
>Call Trace:
> cttimeout_default_fill_info net/netfilter/nfnetlink_cttimeout.c:424 [inline]
> cttimeout_default_get+0x574/0x766 net/netfilter/nfnetlink_cttimeout.c:471
> nfnetlink_rcv_msg+0x544/0x5bd net/netfilter/nfnetlink.c:228
> netlink_rcv_skb+0x1cf/0x2a1 net/netlink/af_netlink.c:2454
> nfnetlink_rcv+0x30f/0x34a net/netfilter/nfnetlink.c:560
> netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
> netlink_unicast+0x3c5/0x4c3 net/netlink/af_netlink.c:1343
> netlink_sendmsg+0x829/0x88e net/netlink/af_netlink.c:1908
> sock_sendmsg_nosec+0x8c/0xad net/socket.c:621
> sock_sendmsg+0x4f/0x60 net/socket.c:631
> ___sys_sendmsg+0x4d6/0x63f net/socket.c:2116
> __sys_sendmsg+0xee/0x17b net/socket.c:2154
> do_syscall_64+0xf8/0x133 arch/x86/entry/common.c:291
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
>* This patch resolves the following conflicts when applying to 4.19:
>- l3num is not used as an argument for cttimeout_default_fill_info() in 4.19
>- nf_icmp_pernet, nf_tcp_pernet, nf_udp_pernet, nf_dccp_pernet,
>nf_icmpv6_pernet, nf_sctp_pernet, nf_generic_pernet do not exist in
>4.19. Expand the usage of those functions into one-liners.
>
>* Tests run: Chrome OS tryjobs, Syzkaller reproducer

I've queued these 2 patches up. It's very nice to see syzkaller running
on -stable kernels, thanks all!

--
Thanks,
Sasha