From f9688b8f6755c3c2eb5c7e2e22ab168d0cb97644 Mon Sep 17 00:00:00 2001
From: Munehisa Kamata <kamatam@amazon.com>
Date: Mon, 26 Oct 2015 19:10:52 -0700
Subject: [PATCH] netfilter: nf_nat_redirect: add missing NULL pointer check
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")
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 97b75f9bfbcd..d43869879fcf 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;
}
--
2.5.0