[RESEND PATCH -stable,4.x.y] netfilter: nf_nat_redirect: add missing NULL pointer check

[RESEND PATCH -stable,4.x.y] netfilter: nf_nat_redirect: add missing NULL pointer check

[Pablo Neira Ayuso]

From: Munehisa Kamata <kamatam@amazon.com>

[ upstream commit 94f9cd81436c85d8c3a318ba92e236ede73752fc ]

Commit 8b13eddfdf04cbfa561725cfc42d6868fe896f56 ("netfilter: refactor NAT
redirect IPv4 to use it from nf_tables") has introduced a trivial logic
change which can result in the following crash.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
IP: [<ffffffffa033002d>] nf_nat_redirect_ipv4+0x2d/0xa0 [nf_nat_redirect]
PGD 3ba662067 PUD 3ba661067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in: ipv6(E) xt_REDIRECT(E) nf_nat_redirect(E) xt_tcpudp(E) iptable_nat(E) nf_conntrack_ipv4(E) nf_defrag_ipv4(E) nf_nat_ipv4(E) nf_nat(E) nf_conntrack(E) ip_tables(E) x_tables(E) binfmt_misc(E) xfs(E) libcrc32c(E) evbug(E) evdev(E) psmouse(E) i2c_piix4(E) i2c_core(E) acpi_cpufreq(E) button(E) ext4(E) crc16(E) jbd2(E) mbcache(E) dm_mirror(E) dm_region_hash(E) dm_log(E) dm_mod(E)
CPU: 0 PID: 2536 Comm: ip Tainted: G            E   4.1.7-15.23.amzn1.x86_64 #1
Hardware name: Xen HVM domU, BIOS 4.2.amazon 05/06/2015
task: ffff8800eb438000 ti: ffff8803ba664000 task.ti: ffff8803ba664000
[...]
Call Trace:
 <IRQ>
 [<ffffffffa0334065>] redirect_tg4+0x15/0x20 [xt_REDIRECT]
 [<ffffffffa02e2e99>] ipt_do_table+0x2b9/0x5e1 [ip_tables]
 [<ffffffffa0328045>] iptable_nat_do_chain+0x25/0x30 [iptable_nat]
 [<ffffffffa031777d>] nf_nat_ipv4_fn+0x13d/0x1f0 [nf_nat_ipv4]
 [<ffffffffa0328020>] ? iptable_nat_ipv4_fn+0x20/0x20 [iptable_nat]
 [<ffffffffa031785e>] nf_nat_ipv4_in+0x2e/0x90 [nf_nat_ipv4]
 [<ffffffffa03280a5>] iptable_nat_ipv4_in+0x15/0x20 [iptable_nat]
 [<ffffffff81449137>] nf_iterate+0x57/0x80
 [<ffffffff814491f7>] nf_hook_slow+0x97/0x100
 [<ffffffff814504d4>] ip_rcv+0x314/0x400

unsigned int
nf_nat_redirect_ipv4(struct sk_buff *skb,
...
{
...
		rcu_read_lock();
		indev = __in_dev_get_rcu(skb->dev);
		if (indev != NULL) {
			ifa = indev->ifa_list;
			newdst = ifa->ifa_local; <---
		}
		rcu_read_unlock();
...
}

Before the commit, 'ifa' had been always checked before access. After the
commit, however, it could be accessed even if it's NULL. Interestingly,
this was once fixed in 2003.

http://marc.info/?l=netfilter-devel&m=106668497403047&w=2

In addition to the original one, we have seen the crash when packets that
need to be redirected somehow arrive on an interface which hasn't been
yet fully configured.

This change just reverts the logic to the old behavior to avoid the crash.

Fixes: 8b13eddfdf04 ("netfilter: refactor NAT redirect IPv4 to use it from nf_tables")
Cc: <stable@vger.kernel.org> # 4.1.x
Cc: <stable@vger.kernel.org> # 4.2.x
Cc: <stable@vger.kernel.org> # 4.3.x
Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_nat_redirect.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_nat_redirect.c b/net/netfilter/nf_nat_redirect.c
index 97b75f9..d438698 100644
--- a/net/netfilter/nf_nat_redirect.c
+++ b/net/netfilter/nf_nat_redirect.c
@@ -55,7 +55,7 @@ nf_nat_redirect_ipv4(struct sk_buff *skb,
 
 		rcu_read_lock();
 		indev = __in_dev_get_rcu(skb->dev);
-		if (indev != NULL) {
+		if (indev && indev->ifa_list) {
 			ifa = indev->ifa_list;
 			newdst = ifa->ifa_local;
 		}
-- 
2.1.4

[RESEND PATCH -stable,4.3.y] netfilter: xt_TEE: fix NULL dereference

[Pablo Neira Ayuso]

From: Eric Dumazet <edumazet@google.com>

[ upstream commit 45efccdbec3cd465c4776ed9ca1d7b1bba1b7e34 ]

iptables -I INPUT ... -j TEE --gateway 10.1.2.3

<crash> because --oif was not specified

tee_tg_check() sets ->priv pointer to NULL in this case.

Fixes: bbde9fc1824a ("netfilter: factor out packet duplication for IPv4/IPv6")
Cc: <stable@vger.kernel.org> # 4.3.x
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/xt_TEE.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index fd980aa..c5fdea1 100644
--- a/net/netfilter/xt_TEE.c
+++ b/net/netfilter/xt_TEE.c
@@ -31,8 +31,9 @@ static unsigned int
 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	const struct xt_tee_tginfo *info = par->targinfo;
+	int oif = info->priv ? info->priv->oif : 0;
 
-	nf_dup_ipv4(skb, par->hooknum, &info->gw.in, info->priv->oif);
+	nf_dup_ipv4(skb, par->hooknum, &info->gw.in, oif);
 
 	return XT_CONTINUE;
 }
@@ -42,8 +43,9 @@ static unsigned int
 tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	const struct xt_tee_tginfo *info = par->targinfo;
+	int oif = info->priv ? info->priv->oif : 0;
 
-	nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, info->priv->oif);
+	nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, oif);
 
 	return XT_CONTINUE;
 }
-- 
2.1.4