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* [PATCH 0/1] Netfilter OOB memory access security patch
@ 2020-07-27 17:57 Will McVicker
  2020-07-27 17:57 ` [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[] Will McVicker
  0 siblings, 1 reply; 7+ messages in thread
From: Will McVicker @ 2020-07-27 17:57 UTC (permalink / raw)
  To: security, Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal
  Cc: David S. Miller, Alexey Kuznetsov, Hideaki YOSHIFUJI,
	netfilter-devel, coreteam, netdev, linux-kernel, kernel-team,
	Will McVicker

Hi,
The attached patch fixes an OOB memory access security bug. The bug is
already fixed in the upstream kernel due to the vulnerable code being
refactored in commit fe2d0020994c ("netfilter: nat: remove
l4proto->in_range") and commit d6c4c8ffb5e5 ("netfilter: nat: remove
l3proto struct"), but the 4.19 and below LTS branches remain vulnerable.
I have verifed the OOB kernel panic is fixed with this patch on both the
4.19 and 4.14 kernels using the approariate hardware.

Please review the fix and apply to branches 4.19.y, 4.14.y, 4.9.y and
4.4.y.

Thanks,
Will

Will McVicker (1):
  netfilter: nat: add range checks for access to nf_nat_l[34]protos[]

 net/ipv4/netfilter/nf_nat_l3proto_ipv4.c |  6 ++++--
 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c |  5 +++--
 net/netfilter/nf_nat_core.c              | 27 ++++++++++++++++++++++--
 net/netfilter/nf_nat_helper.c            |  4 ++++
 4 files changed, 36 insertions(+), 6 deletions(-)

-- 
2.28.0.rc0.142.g3c755180ce-goog


^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[]
  2020-07-27 17:57 [PATCH 0/1] Netfilter OOB memory access security patch Will McVicker
@ 2020-07-27 17:57 ` Will McVicker
  2020-07-29 21:46   ` Pablo Neira Ayuso
  0 siblings, 1 reply; 7+ messages in thread
From: Will McVicker @ 2020-07-27 17:57 UTC (permalink / raw)
  To: security, Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal
  Cc: David S. Miller, Alexey Kuznetsov, Hideaki YOSHIFUJI,
	netfilter-devel, coreteam, netdev, linux-kernel, kernel-team,
	Will McVicker

The indexes to the nf_nat_l[34]protos arrays come from userspace. So we
need to make sure that before indexing the arrays, we verify the index
is within the array bounds in order to prevent an OOB memory access.
Here is an example kernel panic on 4.14.180 when userspace passes in an
index greater than NFPROTO_NUMPROTO.

Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:...
Process poc (pid: 5614, stack limit = 0x00000000a3933121)
CPU: 4 PID: 5614 Comm: poc Tainted: G S      W  O    4.14.180-g051355490483
Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM
task: 000000002a3dfffe task.stack: 00000000a3933121
pc : __cfi_check_fail+0x1c/0x24
lr : __cfi_check_fail+0x1c/0x24
...
Call trace:
__cfi_check_fail+0x1c/0x24
name_to_dev_t+0x0/0x468
nfnetlink_parse_nat_setup+0x234/0x258
ctnetlink_parse_nat_setup+0x4c/0x228
ctnetlink_new_conntrack+0x590/0xc40
nfnetlink_rcv_msg+0x31c/0x4d4
netlink_rcv_skb+0x100/0x184
nfnetlink_rcv+0xf4/0x180
netlink_unicast+0x360/0x770
netlink_sendmsg+0x5a0/0x6a4
___sys_sendmsg+0x314/0x46c
SyS_sendmsg+0xb4/0x108
el0_svc_naked+0x34/0x38

Signed-off-by: Will McVicker <willmcvicker@google.com>
---
 net/ipv4/netfilter/nf_nat_l3proto_ipv4.c |  6 ++++--
 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c |  5 +++--
 net/netfilter/nf_nat_core.c              | 27 ++++++++++++++++++++++--
 net/netfilter/nf_nat_helper.c            |  4 ++++
 4 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
index 6115bf1ff6f0..1912fc66147c 100644
--- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
@@ -218,7 +218,8 @@ int nf_nat_icmp_reply_translation(struct sk_buff *skb,
 		return 1;
 
 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol);
-	if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
+	if (!l4proto ||
+	    !nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
 				   l4proto, &ct->tuplehash[!dir].tuple, !manip))
 		return 0;
 
@@ -234,7 +235,8 @@ int nf_nat_icmp_reply_translation(struct sk_buff *skb,
 	/* Change outer to look like the reply to an incoming packet */
 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0);
-	if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
+	if (!l4proto ||
+	    !nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
 		return 0;
 
 	return 1;
diff --git a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
index ca6d38698b1a..a72840baf27b 100644
--- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
@@ -228,7 +228,8 @@ int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 		return 1;
 
 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
-	if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
+	if (!l4proto ||
+	    !nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 				   l4proto, &ct->tuplehash[!dir].tuple, !manip))
 		return 0;
 
@@ -245,7 +246,7 @@ int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 
 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
-	if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
+	if (!l4proto || !nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 		return 0;
 
 	return 1;
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 2268b10a9dcf..d28185f38955 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -64,12 +64,16 @@ struct nat_net {
 inline const struct nf_nat_l3proto *
 __nf_nat_l3proto_find(u8 family)
 {
+	if (family >= NFPROTO_NUMPROTO)
+		return NULL;
 	return rcu_dereference(nf_nat_l3protos[family]);
 }
 
 inline const struct nf_nat_l4proto *
 __nf_nat_l4proto_find(u8 family, u8 protonum)
 {
+	if (family >= NFPROTO_NUMPROTO)
+		return NULL;
 	return rcu_dereference(nf_nat_l4protos[family][protonum]);
 }
 EXPORT_SYMBOL_GPL(__nf_nat_l4proto_find);
@@ -317,7 +321,7 @@ find_best_ips_proto(const struct nf_conntrack_zone *zone,
  * range. It might not be possible to get a unique tuple, but we try.
  * At worst (or if we race), we will end up with a final duplicate in
  * __ip_conntrack_confirm and drop the packet. */
-static void
+static int
 get_unique_tuple(struct nf_conntrack_tuple *tuple,
 		 const struct nf_conntrack_tuple *orig_tuple,
 		 const struct nf_nat_range2 *range,
@@ -328,13 +332,22 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
 	const struct nf_nat_l3proto *l3proto;
 	const struct nf_nat_l4proto *l4proto;
 	struct net *net = nf_ct_net(ct);
+	int ret = 0;
 
 	zone = nf_ct_zone(ct);
 
 	rcu_read_lock();
 	l3proto = __nf_nat_l3proto_find(orig_tuple->src.l3num);
+	if (!l3proto) {
+		ret = -EINVAL;
+		goto out;
+	}
 	l4proto = __nf_nat_l4proto_find(orig_tuple->src.l3num,
 					orig_tuple->dst.protonum);
+	if (!l4proto) {
+		ret = -EINVAL;
+		goto out;
+	}
 
 	/* 1) If this srcip/proto/src-proto-part is currently mapped,
 	 * and that same mapping gives a unique tuple within the given
@@ -387,6 +400,7 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
 	l4proto->unique_tuple(l3proto, tuple, range, maniptype, ct);
 out:
 	rcu_read_unlock();
+	return ret;
 }
 
 struct nf_conn_nat *nf_ct_nat_ext_add(struct nf_conn *ct)
@@ -409,6 +423,7 @@ nf_nat_setup_info(struct nf_conn *ct,
 {
 	struct net *net = nf_ct_net(ct);
 	struct nf_conntrack_tuple curr_tuple, new_tuple;
+	int err;
 
 	/* Can't setup nat info for confirmed ct. */
 	if (nf_ct_is_confirmed(ct))
@@ -428,7 +443,9 @@ nf_nat_setup_info(struct nf_conn *ct,
 	nf_ct_invert_tuplepr(&curr_tuple,
 			     &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 
-	get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype);
+	err = get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype);
+	if (err < 0)
+		return NF_DROP;
 
 	if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) {
 		struct nf_conntrack_tuple reply;
@@ -509,8 +526,12 @@ static unsigned int nf_nat_manip_pkt(struct sk_buff *skb, struct nf_conn *ct,
 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 
 	l3proto = __nf_nat_l3proto_find(target.src.l3num);
+	if (!l3proto)
+		return NF_DROP;
 	l4proto = __nf_nat_l4proto_find(target.src.l3num,
 					target.dst.protonum);
+	if (!l4proto)
+		return NF_DROP;
 	if (!l3proto->manip_pkt(skb, 0, l4proto, &target, mtype))
 		return NF_DROP;
 
@@ -816,6 +837,8 @@ static int nfnetlink_parse_nat_proto(struct nlattr *attr,
 		return err;
 
 	l4proto = __nf_nat_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
+	if (!l4proto)
+		return -EINVAL;
 	if (l4proto->nlattr_to_range)
 		err = l4proto->nlattr_to_range(tb, range);
 
diff --git a/net/netfilter/nf_nat_helper.c b/net/netfilter/nf_nat_helper.c
index 99606baedda4..6f694444137e 100644
--- a/net/netfilter/nf_nat_helper.c
+++ b/net/netfilter/nf_nat_helper.c
@@ -121,6 +121,8 @@ bool __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
 	datalen = skb->len - protoff;
 
 	l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
+	if (!l3proto)
+		return false;
 	l3proto->csum_recalc(skb, IPPROTO_TCP, tcph, &tcph->check,
 			     datalen, oldlen);
 
@@ -179,6 +181,8 @@ nf_nat_mangle_udp_packet(struct sk_buff *skb,
 		return true;
 
 	l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
+	if (!l3proto)
+		return false;
 	l3proto->csum_recalc(skb, IPPROTO_UDP, udph, &udph->check,
 			     datalen, oldlen);
 
-- 
2.28.0.rc0.142.g3c755180ce-goog


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[]
  2020-07-27 17:57 ` [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[] Will McVicker
@ 2020-07-29 21:46   ` Pablo Neira Ayuso
  2020-07-31  0:26     ` William Mcvicker
  0 siblings, 1 reply; 7+ messages in thread
From: Pablo Neira Ayuso @ 2020-07-29 21:46 UTC (permalink / raw)
  To: Will McVicker
  Cc: security, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Alexey Kuznetsov, Hideaki YOSHIFUJI, netfilter-devel, coreteam,
	netdev, linux-kernel, kernel-team

Hi Will,

On Mon, Jul 27, 2020 at 05:57:20PM +0000, Will McVicker wrote:
> The indexes to the nf_nat_l[34]protos arrays come from userspace. So we
> need to make sure that before indexing the arrays, we verify the index
> is within the array bounds in order to prevent an OOB memory access.
> Here is an example kernel panic on 4.14.180 when userspace passes in an
> index greater than NFPROTO_NUMPROTO.
> 
> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> Modules linked in:...
> Process poc (pid: 5614, stack limit = 0x00000000a3933121)
> CPU: 4 PID: 5614 Comm: poc Tainted: G S      W  O    4.14.180-g051355490483
> Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM
> task: 000000002a3dfffe task.stack: 00000000a3933121
> pc : __cfi_check_fail+0x1c/0x24
> lr : __cfi_check_fail+0x1c/0x24
> ...
> Call trace:
> __cfi_check_fail+0x1c/0x24
> name_to_dev_t+0x0/0x468
> nfnetlink_parse_nat_setup+0x234/0x258

If this oops is only triggerable from userspace, I think a sanity
check in nfnetlink_parse_nat_setup should suffice to reject
unsupported layer 3 and layer 4 protocols.

I mean, in this patch I see more chunks in the packet path, such as
nf_nat_l3proto_ipv4 that should never happen. I would just fix the
userspace ctnetlink path.

BTW, do you have a Fixes: tag for this? This will be useful for
-stable maintainer to pick up this fix.

Thanks.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[]
  2020-07-29 21:46   ` Pablo Neira Ayuso
@ 2020-07-31  0:26     ` William Mcvicker
  2020-07-31 17:51       ` Pablo Neira Ayuso
  0 siblings, 1 reply; 7+ messages in thread
From: William Mcvicker @ 2020-07-31  0:26 UTC (permalink / raw)
  To: Pablo Neira Ayuso
  Cc: security, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Alexey Kuznetsov, Hideaki YOSHIFUJI, netfilter-devel, coreteam,
	netdev, linux-kernel, kernel-team

Hi Pablo,

Yes, I believe this oops is only triggered by userspace when the user
specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work
the patch to check for this in ctnetlink_create_conntrack().

> BTW, do you have a Fixes: tag for this? This will be useful for
> -stable maintainer to pick up this fix.

Regarding the Fixes: tag, I don't have one offhand since this bug was reported
to me, but I can search through the code history to find the commit that
exposed this vulnerability.

Thanks,
Will

On 07/29/2020, Pablo Neira Ayuso wrote:
> Hi Will,
> 
> On Mon, Jul 27, 2020 at 05:57:20PM +0000, Will McVicker wrote:
> > The indexes to the nf_nat_l[34]protos arrays come from userspace. So we
> > need to make sure that before indexing the arrays, we verify the index
> > is within the array bounds in order to prevent an OOB memory access.
> > Here is an example kernel panic on 4.14.180 when userspace passes in an
> > index greater than NFPROTO_NUMPROTO.
> > 
> > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> > Modules linked in:...
> > Process poc (pid: 5614, stack limit = 0x00000000a3933121)
> > CPU: 4 PID: 5614 Comm: poc Tainted: G S      W  O    4.14.180-g051355490483
> > Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM
> > task: 000000002a3dfffe task.stack: 00000000a3933121
> > pc : __cfi_check_fail+0x1c/0x24
> > lr : __cfi_check_fail+0x1c/0x24
> > ...
> > Call trace:
> > __cfi_check_fail+0x1c/0x24
> > name_to_dev_t+0x0/0x468
> > nfnetlink_parse_nat_setup+0x234/0x258
> 
> If this oops is only triggerable from userspace, I think a sanity
> check in nfnetlink_parse_nat_setup should suffice to reject
> unsupported layer 3 and layer 4 protocols.
> 
> I mean, in this patch I see more chunks in the packet path, such as
> nf_nat_l3proto_ipv4 that should never happen. I would just fix the
> userspace ctnetlink path.
> 
> BTW, do you have a Fixes: tag for this? This will be useful for
> -stable maintainer to pick up this fix.
> 
> Thanks.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[]
  2020-07-31  0:26     ` William Mcvicker
@ 2020-07-31 17:51       ` Pablo Neira Ayuso
  2020-07-31 18:16         ` William Mcvicker
  0 siblings, 1 reply; 7+ messages in thread
From: Pablo Neira Ayuso @ 2020-07-31 17:51 UTC (permalink / raw)
  To: William Mcvicker
  Cc: security, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Alexey Kuznetsov, Hideaki YOSHIFUJI, netfilter-devel, coreteam,
	netdev, linux-kernel, kernel-team

Hi William,

On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote:
> Hi Pablo,
> 
> Yes, I believe this oops is only triggered by userspace when the user
> specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work
> the patch to check for this in ctnetlink_create_conntrack().

Great.

Note that this code does not exist in the tree anymore. I'm not sure
if this problem still exists upstream, this patch does not apply to
nf.git. This fix should only go for -stable maintainers.

> > BTW, do you have a Fixes: tag for this? This will be useful for
> > -stable maintainer to pick up this fix.
> 
> Regarding the Fixes: tag, I don't have one offhand since this bug was reported
> to me, but I can search through the code history to find the commit that
> exposed this vulnerability.

That would be great.

Thank you.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[]
  2020-07-31 17:51       ` Pablo Neira Ayuso
@ 2020-07-31 18:16         ` William Mcvicker
  2020-08-03 18:31           ` [PATCH v2 1/1] netfilter: nat: add a range check for l3/l4 protonum William Mcvicker
  0 siblings, 1 reply; 7+ messages in thread
From: William Mcvicker @ 2020-07-31 18:16 UTC (permalink / raw)
  To: Pablo Neira Ayuso
  Cc: security, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Alexey Kuznetsov, Hideaki YOSHIFUJI, netfilter-devel, coreteam,
	netdev, linux-kernel, kernel-team

Hi Pablo,

> Note that this code does not exist in the tree anymore. I'm not sure
> if this problem still exists upstream, this patch does not apply to
> nf.git. This fix should only go for -stable maintainers.

Right, the vulnerability has been fixed by the refactor commit fe2d0020994cd
("netfilter: nat: remove l4proto->in_range"), but this patch is a part of
a full re-work of the code and doesn't backport very cleanly to the LTS
branches. So this fix is only applicable to the 4.19, 4.14, 4.9, and 4.4 LTS
branches. I missed the -stable email, but will re-add it to this thread with
the re-worked patch.

Thanks,
Will

On 07/31/2020, Pablo Neira Ayuso wrote:
> Hi William,
> 
> On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote:
> > Hi Pablo,
> > 
> > Yes, I believe this oops is only triggered by userspace when the user
> > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work
> > the patch to check for this in ctnetlink_create_conntrack().
> 
> Great.
> 
> Note that this code does not exist in the tree anymore. I'm not sure
> if this problem still exists upstream, this patch does not apply to
> nf.git. This fix should only go for -stable maintainers.
> 
> > > BTW, do you have a Fixes: tag for this? This will be useful for
> > > -stable maintainer to pick up this fix.
> > 
> > Regarding the Fixes: tag, I don't have one offhand since this bug was reported
> > to me, but I can search through the code history to find the commit that
> > exposed this vulnerability.
> 
> That would be great.
> 
> Thank you.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH v2 1/1] netfilter: nat: add a range check for l3/l4 protonum
  2020-07-31 18:16         ` William Mcvicker
@ 2020-08-03 18:31           ` William Mcvicker
  0 siblings, 0 replies; 7+ messages in thread
From: William Mcvicker @ 2020-08-03 18:31 UTC (permalink / raw)
  To: Pablo Neira Ayuso
  Cc: security, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Alexey Kuznetsov, Hideaki YOSHIFUJI, netfilter-devel, coreteam,
	netdev, linux-kernel, kernel-team, stable


[-- Attachment #1: Type: text/plain, Size: 1799 bytes --]

Hi,

I have attached the follow up fix that checks for the proto index during
conntrack creation.

Thanks,
Will

On 07/31/2020, William Mcvicker wrote:
> Hi Pablo,
> 
> > Note that this code does not exist in the tree anymore. I'm not sure
> > if this problem still exists upstream, this patch does not apply to
> > nf.git. This fix should only go for -stable maintainers.
> 
> Right, the vulnerability has been fixed by the refactor commit fe2d0020994cd
> ("netfilter: nat: remove l4proto->in_range"), but this patch is a part of
> a full re-work of the code and doesn't backport very cleanly to the LTS
> branches. So this fix is only applicable to the 4.19, 4.14, 4.9, and 4.4 LTS
> branches. I missed the -stable email, but will re-add it to this thread with
> the re-worked patch.
> 
> Thanks,
> Will
> 
> On 07/31/2020, Pablo Neira Ayuso wrote:
> > Hi William,
> > 
> > On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote:
> > > Hi Pablo,
> > > 
> > > Yes, I believe this oops is only triggered by userspace when the user
> > > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work
> > > the patch to check for this in ctnetlink_create_conntrack().
> > 
> > Great.
> > 
> > Note that this code does not exist in the tree anymore. I'm not sure
> > if this problem still exists upstream, this patch does not apply to
> > nf.git. This fix should only go for -stable maintainers.
> > 
> > > > BTW, do you have a Fixes: tag for this? This will be useful for
> > > > -stable maintainer to pick up this fix.
> > > 
> > > Regarding the Fixes: tag, I don't have one offhand since this bug was reported
> > > to me, but I can search through the code history to find the commit that
> > > exposed this vulnerability.
> > 
> > That would be great.
> > 
> > Thank you.

[-- Attachment #2: 0001-netfilter-nat-add-a-range-check-for-l3-l4-protonum.patch --]
[-- Type: text/x-diff, Size: 2041 bytes --]

From 2a9d621fa5c225e6aece6b4622a9a816c6fcfa0d Mon Sep 17 00:00:00 2001
From: Will McVicker <willmcvicker@google.com>
Date: Fri, 31 Jul 2020 13:10:43 -0700
Subject: [PATCH] netfilter: nat: add a range check for l3/l4 protonum

The indexes to the nf_nat_l[34]protos arrays come from userspace. So
check the tuple's family, e.g. l3num, when creating the conntrack in
order to prevent an OOB memory access during setup.  Here is an example
kernel panic on 4.14.180 when userspace passes in an index greater than
NFPROTO_NUMPROTO.

Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:...
Process poc (pid: 5614, stack limit = 0x00000000a3933121)
CPU: 4 PID: 5614 Comm: poc Tainted: G S      W  O    4.14.180-g051355490483
Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM
task: 000000002a3dfffe task.stack: 00000000a3933121
pc : __cfi_check_fail+0x1c/0x24
lr : __cfi_check_fail+0x1c/0x24
...
Call trace:
__cfi_check_fail+0x1c/0x24
name_to_dev_t+0x0/0x468
nfnetlink_parse_nat_setup+0x234/0x258
ctnetlink_parse_nat_setup+0x4c/0x228
ctnetlink_new_conntrack+0x590/0xc40
nfnetlink_rcv_msg+0x31c/0x4d4
netlink_rcv_skb+0x100/0x184
nfnetlink_rcv+0xf4/0x180
netlink_unicast+0x360/0x770
netlink_sendmsg+0x5a0/0x6a4
___sys_sendmsg+0x314/0x46c
SyS_sendmsg+0xb4/0x108
el0_svc_naked+0x34/0x38

Fixes: c1d10adb4a521 ("[NETFILTER]: Add ctnetlink port for nf_conntrack")
Signed-off-by: Will McVicker <willmcvicker@google.com>
---
 net/netfilter/nf_conntrack_netlink.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 31fa94064a62..56d310f8b29a 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1129,6 +1129,8 @@ ctnetlink_parse_tuple(const struct nlattr * const cda[],
 	if (!tb[CTA_TUPLE_IP])
 		return -EINVAL;
 
+	if (l3num >= NFPROTO_NUMPROTO)
+		return -EINVAL;
 	tuple->src.l3num = l3num;
 
 	err = ctnetlink_parse_tuple_ip(tb[CTA_TUPLE_IP], tuple);
-- 
2.28.0.163.g6104cc2f0b6-goog


^ permalink raw reply	[flat|nested] 7+ messages in thread

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Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-27 17:57 [PATCH 0/1] Netfilter OOB memory access security patch Will McVicker
2020-07-27 17:57 ` [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat_l[34]protos[] Will McVicker
2020-07-29 21:46   ` Pablo Neira Ayuso
2020-07-31  0:26     ` William Mcvicker
2020-07-31 17:51       ` Pablo Neira Ayuso
2020-07-31 18:16         ` William Mcvicker
2020-08-03 18:31           ` [PATCH v2 1/1] netfilter: nat: add a range check for l3/l4 protonum William Mcvicker

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