[PATCH 0/8] Netfilter fixes for net

[PATCH 0/8] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi David,

The following patchset contains Netfilter fixes for your net tree,
they are:

1) Revisit warning logic when not applying default helper assignment.
   Jiri Kosina considers we are breaking existing setups and not warning
   our users accordinly now that automatic helper assignment has been
   turned off by default. So let's make him happy by spotting the warning
   by when we find a helper but we cannot attach, instead of warning on the
   former deprecated behaviour. Patch from Jiri Kosina.

2) Two patches to fix regression in ctnetlink interfaces with
   nfnetlink_queue. Specifically, perform more relaxed in CTA_STATUS
   and do not bail out if CTA_HELP indicates the same helper that we
   already have. Patches from Kevin Cernekee.

3) A couple of bugfixes for ipset via Jozsef Kadlecsik. Due to wrong
   index logic in hash set types and null pointer exception in the
   list:set type.

4) hashlimit bails out with correct userspace parameters due to wrong
   arithmetics in the code that avoids "divide by zero" when
   transforming the userspace timing in milliseconds to token credits.
   Patch from Alban Browaeys.

5) Fix incorrect NFQA_VLAN_MAX definition, patch from
   Ken-ichirou MATSUZAWA.

6) Don't not declare nfnetlink batch error list as static, since this
   may be used by several subsystems at the same time. Patch from
   Liping Zhang.

You can pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git

Thanks!

----------------------------------------------------------------

The following changes since commit cafe8df8b9bc9aa3dffa827c1a6757c6cd36f657:

  net: phy: Fix lack of reference count on PHY driver (2017-02-02 22:59:43 -0500)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git HEAD

for you to fetch changes up to 3ef767e5cbd405abfd01339c7e5daaf98e037be2:

  Merge branch 'master' of git://blackhole.kfki.hu/nf (2017-02-21 14:01:05 +0100)

----------------------------------------------------------------
Alban Browaeys (1):
      netfilter: xt_hashlimit: Fix integer divide round to zero.

Jiri Kosina (1):
      netfilter: nf_ct_helper: warn when not applying default helper assignment

Jozsef Kadlecsik (1):
      Fix bug: sometimes valid entries in hash:* types of sets were evicted

Ken-ichirou MATSUZAWA (1):
      netfilter: nfnetlink_queue: fix NFQA_VLAN_MAX definition

Kevin Cernekee (2):
      netfilter: ctnetlink: Fix regression in CTA_STATUS processing
      netfilter: ctnetlink: Fix regression in CTA_HELP processing

Liping Zhang (1):
      netfilter: nfnetlink: remove static declaration from err_list

Pablo Neira Ayuso (1):
      Merge branch 'master' of git://blackhole.kfki.hu/nf

Vishwanath Pai (1):
      netfilter: ipset: Null pointer exception in ipset list:set

 include/uapi/linux/netfilter/nf_conntrack_common.h |  4 ++
 include/uapi/linux/netfilter/nfnetlink_queue.h     |  2 +-
 net/netfilter/ipset/ip_set_hash_gen.h              |  2 +-
 net/netfilter/ipset/ip_set_list_set.c              |  9 +++--
 net/netfilter/nf_conntrack_helper.c                | 39 +++++++++++++-------
 net/netfilter/nf_conntrack_netlink.c               | 43 +++++++++++++++++++---
 net/netfilter/nfnetlink.c                          |  2 +-
 net/netfilter/xt_hashlimit.c                       | 25 +++++--------
 8 files changed, 86 insertions(+), 40 deletions(-)

[PATCH 1/8] netfilter: nf_ct_helper: warn when not applying default helper assignment

[Pablo Neira Ayuso]

From: Jiri Kosina <jkosina@suse.cz>

Commit 3bb398d925 ("netfilter: nf_ct_helper: disable automatic helper
assignment") is causing behavior regressions in firewalls, as traffic
handled by conntrack helpers is now by default not passed through even
though it was before due to missing CT targets (which were not necessary
before this commit).

The default had to be switched off due to security reasons [1] [2] and
therefore should stay the way it is, but let's be friendly to firewall
admins and issue a warning the first time we're in situation where packet
would be likely passed through with the old default but we're likely going
to drop it on the floor now.

Rewrite the code a little bit as suggested by Linus, so that we avoid
spaghettiing the code even more -- namely the whole decision making
process regarding helper selection (either automatic or not) is being
separated, so that the whole logic can be simplified and code (condition)
duplication reduced.

[1] https://cansecwest.com/csw12/conntrack-attack.pdf
[2] https://home.regit.org/netfilter-en/secure-use-of-helpers/

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_conntrack_helper.c | 39 ++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 7341adf7059d..6dc44d9b4190 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -188,6 +188,26 @@ nf_ct_helper_ext_add(struct nf_conn *ct,
 }
 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 
+static struct nf_conntrack_helper *
+nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
+{
+	if (!net->ct.sysctl_auto_assign_helper) {
+		if (net->ct.auto_assign_helper_warned)
+			return NULL;
+		if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
+			return NULL;
+		pr_info("nf_conntrack: default automatic helper assignment "
+			"has been turned off for security reasons and CT-based "
+			" firewall rule not found. Use the iptables CT target "
+			"to attach helpers instead.\n");
+		net->ct.auto_assign_helper_warned = 1;
+		return NULL;
+	}
+
+	return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+}
+
+
 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 			      gfp_t flags)
 {
@@ -213,21 +233,14 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 	}
 
 	help = nfct_help(ct);
-	if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
-		helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
-		if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
-			pr_info("nf_conntrack: automatic helper "
-				"assignment is deprecated and it will "
-				"be removed soon. Use the iptables CT target "
-				"to attach helpers instead.\n");
-			net->ct.auto_assign_helper_warned = true;
-		}
-	}
 
 	if (helper == NULL) {
-		if (help)
-			RCU_INIT_POINTER(help->helper, NULL);
-		return 0;
+		helper = nf_ct_lookup_helper(ct, net);
+		if (helper == NULL) {
+			if (help)
+				RCU_INIT_POINTER(help->helper, NULL);
+			return 0;
+		}
 	}
 
 	if (help == NULL) {
-- 
2.1.4

[PATCH 2/8] netfilter: ctnetlink: Fix regression in CTA_STATUS processing

[Pablo Neira Ayuso]

From: Kevin Cernekee <cernekee@chromium.org>

The libnetfilter_conntrack userland library always sets IPS_CONFIRMED
when building a CTA_STATUS attribute.  If this toggles the bit from
0->1, the parser will return an error.  On Linux 4.4+ this will cause any
NFQA_EXP attribute in the packet to be ignored.  This breaks conntrackd's
userland helpers because they operate on unconfirmed connections.

Instead of returning -EBUSY if the user program asks to modify an
unchangeable bit, simply ignore the change.

Also, fix the logic so that user programs are allowed to clear
the bits that they are allowed to change.

Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/uapi/linux/netfilter/nf_conntrack_common.h |  4 ++++
 net/netfilter/nf_conntrack_netlink.c               | 26 +++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/netfilter/nf_conntrack_common.h b/include/uapi/linux/netfilter/nf_conntrack_common.h
index 6d074d14ee27..6a8e33dd4ecb 100644
--- a/include/uapi/linux/netfilter/nf_conntrack_common.h
+++ b/include/uapi/linux/netfilter/nf_conntrack_common.h
@@ -82,6 +82,10 @@ enum ip_conntrack_status {
 	IPS_DYING_BIT = 9,
 	IPS_DYING = (1 << IPS_DYING_BIT),
 
+	/* Bits that cannot be altered from userland. */
+	IPS_UNCHANGEABLE_MASK = (IPS_NAT_DONE_MASK | IPS_NAT_MASK |
+				 IPS_EXPECTED | IPS_CONFIRMED | IPS_DYING),
+
 	/* Connection has fixed timeout. */
 	IPS_FIXED_TIMEOUT_BIT = 10,
 	IPS_FIXED_TIMEOUT = (1 << IPS_FIXED_TIMEOUT_BIT),
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 27540455dc62..bf04b7e9d6f7 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -2270,6 +2270,30 @@ ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct,
 }
 
 static int
+ctnetlink_update_status(struct nf_conn *ct, const struct nlattr * const cda[])
+{
+	unsigned int status = ntohl(nla_get_be32(cda[CTA_STATUS]));
+	unsigned long d = ct->status ^ status;
+
+	if (d & IPS_SEEN_REPLY && !(status & IPS_SEEN_REPLY))
+		/* SEEN_REPLY bit can only be set */
+		return -EBUSY;
+
+	if (d & IPS_ASSURED && !(status & IPS_ASSURED))
+		/* ASSURED bit can only be set */
+		return -EBUSY;
+
+	/* This check is less strict than ctnetlink_change_status()
+	 * because callers often flip IPS_EXPECTED bits when sending
+	 * an NFQA_CT attribute to the kernel.  So ignore the
+	 * unchangeable bits but do not error out.
+	 */
+	ct->status = (status & ~IPS_UNCHANGEABLE_MASK) |
+		     (ct->status & IPS_UNCHANGEABLE_MASK);
+	return 0;
+}
+
+static int
 ctnetlink_glue_parse_ct(const struct nlattr *cda[], struct nf_conn *ct)
 {
 	int err;
@@ -2280,7 +2304,7 @@ ctnetlink_glue_parse_ct(const struct nlattr *cda[], struct nf_conn *ct)
 			return err;
 	}
 	if (cda[CTA_STATUS]) {
-		err = ctnetlink_change_status(ct, cda);
+		err = ctnetlink_update_status(ct, cda);
 		if (err < 0)
 			return err;
 	}
-- 
2.1.4

[PATCH 3/8] netfilter: ctnetlink: Fix regression in CTA_HELP processing

[Pablo Neira Ayuso]

From: Kevin Cernekee <cernekee@chromium.org>

Prior to Linux 4.4, it was usually harmless to send a CTA_HELP attribute
containing the name of the current helper.  That is no longer the case:
as of Linux 4.4, if ctnetlink_change_helper() returns an error from
the ct->master check, processing of the request will fail, skipping the
NFQA_EXP attribute (if present).

This patch changes the behavior to improve compatibility with user
programs that expect the kernel interface to work the way it did prior
to Linux 4.4.  If a user program specifies CTA_HELP but the argument
matches the current conntrack helper name, ignore it instead of generating
an error.

Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_conntrack_netlink.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index bf04b7e9d6f7..6806b5e73567 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1478,14 +1478,23 @@ static int ctnetlink_change_helper(struct nf_conn *ct,
 	struct nlattr *helpinfo = NULL;
 	int err;
 
-	/* don't change helper of sibling connections */
-	if (ct->master)
-		return -EBUSY;
-
 	err = ctnetlink_parse_help(cda[CTA_HELP], &helpname, &helpinfo);
 	if (err < 0)
 		return err;
 
+	/* don't change helper of sibling connections */
+	if (ct->master) {
+		/* If we try to change the helper to the same thing twice,
+		 * treat the second attempt as a no-op instead of returning
+		 * an error.
+		 */
+		if (help && help->helper &&
+		    !strcmp(help->helper->name, helpname))
+			return 0;
+		else
+			return -EBUSY;
+	}
+
 	if (!strcmp(helpname, "")) {
 		if (help && help->helper) {
 			/* we had a helper before ... */
-- 
2.1.4

[PATCH 4/8] Fix bug: sometimes valid entries in hash:* types of sets were evicted

[Pablo Neira Ayuso]

From: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

Wrong index was used and therefore when shrinking a hash bucket at
deleting an entry, valid entries could be evicted as well.
Thanks to Eric Ewanco for the thorough bugreport.

Fixes netfilter bugzilla #1119

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
---
 net/netfilter/ipset/ip_set_hash_gen.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h
index 1b05d4a7d5a1..f236c0bc7b3f 100644
--- a/net/netfilter/ipset/ip_set_hash_gen.h
+++ b/net/netfilter/ipset/ip_set_hash_gen.h
@@ -897,7 +897,7 @@ mtype_del(struct ip_set *set, void *value, const struct ip_set_ext *ext,
 					continue;
 				data = ahash_data(n, j, dsize);
 				memcpy(tmp->value + k * dsize, data, dsize);
-				set_bit(j, tmp->used);
+				set_bit(k, tmp->used);
 				k++;
 			}
 			tmp->pos = k;
-- 
2.1.4

[PATCH 5/8] netfilter: ipset: Null pointer exception in ipset list:set

[Pablo Neira Ayuso]

From: Vishwanath Pai <vpai@akamai.com>

If we use before/after to add an element to an empty list it will cause
a kernel panic.

$> cat crash.restore
create a hash:ip
create b hash:ip
create test list:set timeout 5 size 4
add test b before a

$> ipset -R < crash.restore

Executing the above will crash the kernel.

Signed-off-by: Vishwanath Pai <vpai@akamai.com>
Reviewed-by: Josh Hunt <johunt@akamai.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
---
 net/netfilter/ipset/ip_set_list_set.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/ipset/ip_set_list_set.c b/net/netfilter/ipset/ip_set_list_set.c
index 51077c53d76b..178d4eba013b 100644
--- a/net/netfilter/ipset/ip_set_list_set.c
+++ b/net/netfilter/ipset/ip_set_list_set.c
@@ -260,11 +260,14 @@ list_set_uadd(struct ip_set *set, void *value, const struct ip_set_ext *ext,
 		else
 			prev = e;
 	}
+
+	/* If before/after is used on an empty set */
+	if ((d->before > 0 && !next) ||
+	    (d->before < 0 && !prev))
+		return -IPSET_ERR_REF_EXIST;
+
 	/* Re-add already existing element */
 	if (n) {
-		if ((d->before > 0 && !next) ||
-		    (d->before < 0 && !prev))
-			return -IPSET_ERR_REF_EXIST;
 		if (!flag_exist)
 			return -IPSET_ERR_EXIST;
 		/* Update extensions */
-- 
2.1.4

[PATCH 6/8] netfilter: xt_hashlimit: Fix integer divide round to zero.

[Pablo Neira Ayuso]

From: Alban Browaeys <alban.browaeys@gmail.com>

Diving the divider by the multiplier before applying to the input.
When this would "divide by zero", divide the multiplier by the divider
first then multiply the input by this value.

Currently user2creds outputs zero when input value is bigger than the
number of slices and  lower than scale.
This as then user input is applied an integer divide operation to
a number greater than itself (scale).
That rounds up to zero, then we multiply zero by the credits slice size.

  iptables -t filter -I INPUT --protocol tcp --match hashlimit
  --hashlimit 40/second --hashlimit-burst 20 --hashlimit-mode srcip
  --hashlimit-name syn-flood --jump RETURN

thus trigger the overflow detection code:

xt_hashlimit: overflow, try lower: 25000/20

(25000 as hashlimit avg and 20 the burst)

Here:
134217 slices of (HZ * CREDITS_PER_JIFFY) size.
500000 is user input value
1000000 is XT_HASHLIMIT_SCALE_v2
gives: 0 as user2creds output
Setting burst to "1" typically solve the issue ...
but setting it to "40" does too !

This is on 32bit arch calling into revision 2 of hashlimit.

Signed-off-by: Alban Browaeys <alban.browaeys@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/xt_hashlimit.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 10063408141d..84ad5ab34558 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -463,23 +463,16 @@ static u32 xt_hashlimit_len_to_chunks(u32 len)
 /* Precision saver. */
 static u64 user2credits(u64 user, int revision)
 {
-	if (revision == 1) {
-		/* If multiplying would overflow... */
-		if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1))
-			/* Divide first. */
-			return div64_u64(user, XT_HASHLIMIT_SCALE)
-				* HZ * CREDITS_PER_JIFFY_v1;
-
-		return div64_u64(user * HZ * CREDITS_PER_JIFFY_v1,
-				 XT_HASHLIMIT_SCALE);
-	} else {
-		if (user > 0xFFFFFFFFFFFFFFFFULL / (HZ*CREDITS_PER_JIFFY))
-			return div64_u64(user, XT_HASHLIMIT_SCALE_v2)
-				* HZ * CREDITS_PER_JIFFY;
+	u64 scale = (revision == 1) ?
+		XT_HASHLIMIT_SCALE : XT_HASHLIMIT_SCALE_v2;
+	u64 cpj = (revision == 1) ?
+		CREDITS_PER_JIFFY_v1 : CREDITS_PER_JIFFY;
 
-		return div64_u64(user * HZ * CREDITS_PER_JIFFY,
-				 XT_HASHLIMIT_SCALE_v2);
-	}
+	/* Avoid overflow: divide the constant operands first */
+	if (scale >= HZ * cpj)
+		return div64_u64(user, div64_u64(scale, HZ * cpj));
+
+	return user * div64_u64(HZ * cpj, scale);
 }
 
 static u32 user2credits_byte(u32 user)
-- 
2.1.4

[PATCH 7/8] netfilter: nfnetlink_queue: fix NFQA_VLAN_MAX definition

[Pablo Neira Ayuso]

From: Ken-ichirou MATSUZAWA <chamaken@gmail.com>

Should be - 1 as in other _MAX definitions.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/uapi/linux/netfilter/nfnetlink_queue.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/netfilter/nfnetlink_queue.h b/include/uapi/linux/netfilter/nfnetlink_queue.h
index ae30841ff94e..d42f0396fe30 100644
--- a/include/uapi/linux/netfilter/nfnetlink_queue.h
+++ b/include/uapi/linux/netfilter/nfnetlink_queue.h
@@ -36,7 +36,7 @@ enum nfqnl_vlan_attr {
 	NFQA_VLAN_TCI,			/* __be16 skb htons(vlan_tci) */
 	__NFQA_VLAN_MAX,
 };
-#define NFQA_VLAN_MAX (__NFQA_VLAN_MAX + 1)
+#define NFQA_VLAN_MAX (__NFQA_VLAN_MAX - 1)
 
 enum nfqnl_attr_type {
 	NFQA_UNSPEC,
-- 
2.1.4

[PATCH 8/8] netfilter: nfnetlink: remove static declaration from err_list

[Pablo Neira Ayuso]

From: Liping Zhang <zlpnobody@gmail.com>

Otherwise, different subsys will race to access the err_list, with holding
the different nfnl_lock(subsys_id).

But this will not happen now, since ->call_batch is only implemented by
nftables, so the err_list is protected by nfnl_lock(NFNL_SUBSYS_NFTABLES).

Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nfnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index a09fa9fd8f3d..6fa448478cba 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -279,7 +279,7 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net *net = sock_net(skb->sk);
 	const struct nfnetlink_subsystem *ss;
 	const struct nfnl_callback *nc;
-	static LIST_HEAD(err_list);
+	LIST_HEAD(err_list);
 	u32 status;
 	int err;
 
-- 
2.1.4

Re: [PATCH 0/8] Netfilter fixes for net

[David Miller]

From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Thu, 23 Feb 2017 12:14:01 +0100

> The following patchset contains Netfilter fixes for your net tree,
> they are:
 ...
> You can pull these changes from:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git

Pulled, thanks a lot!