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netfilter: nf_nat_redirect: add missing NULL pointer check (CVE-2015-8787)

This commit is contained in:
Salvatore Bonaccorso 2016-01-27 19:24:21 +01:00
parent 76c256b5b8
commit b1fa3fac88
3 changed files with 83 additions and 0 deletions
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1
debian/changelog vendored
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@ -57,6 +57,7 @@ linux (4.3.4-1) UNRELEASED; urgency=medium
[ Salvatore Bonaccorso ]
* tcp: fix zero cwnd in tcp_cwnd_reduction (CVE-2016-2070)
* netfilter: nf_nat_redirect: add missing NULL pointer check (CVE-2015-8787)
-- Ben Hutchings <ben@decadent.org.uk> Sat, 23 Jan 2016 11:51:46 +0000

81
debian/patches/bugfix/all/netfilter-nf_nat_redirect-add-missing-NULL-pointer-c.patch vendored Normal file
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@ -0,0 +1,81 @@
From: Munehisa Kamata <kamatam@amazon.com>
Date: Mon, 26 Oct 2015 19:10:52 -0700
Subject: netfilter: nf_nat_redirect: add missing NULL pointer check
Origin: https://git.kernel.org/linus/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 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;
}
--
2.7.0

1
debian/patches/series vendored
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@ -143,3 +143,4 @@ bugfix/all/bcache-change-refill_dirty-to-always-scan-entire-dis.patch
bugfix/all/fuse-break-infinite-loop-in-fuse_fill_write_pages.patch
bugfix/all/tcp-fix-zero-cwnd-in-tcp_cwnd_reduction.patch
bugfix/all/scsi-fix-crashes-in-sd-and-sr-runtime-pm.patch
bugfix/all/netfilter-nf_nat_redirect-add-missing-NULL-pointer-c.patch