Subject: [PATCH v3 19/30] inet: frags: fix ip6frag_low_thresh boundary

From: Stephen Hemminger <[email-masked]>
Date: Thu, 13 Sep 2018 07:58:51 -0700

From: Eric Dumazet <[email-masked]>

Giving an integer to proc_doulongvec_minmax() is dangerous on 64bit arches,
since linker might place next to it a non zero value preventing a change
to ip6frag_low_thresh.

ip6frag_low_thresh is not used anymore in the kernel, but we do not
want to prematuraly break user scripts wanting to change it.

Since specifying a minimal value of 0 for proc_doulongvec_minmax()
is moot, let's remove these zero values in all defrag units.

Fixes: 6e00f7dd5e4e ("ipv6: frags: fix /proc/sys/net/ipv6/ip6frag_low_thresh")
Signed-off-by: Eric Dumazet <[email-masked]>
Reported-by: Maciej Żenczykowski <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
(cherry picked from commit 3d23401283e80ceb03f765842787e0e79ff598b7)
---
 net/ieee802154/6lowpan/reassembly.c     | 2 --
 net/ipv4/ip_fragment.c                  | 5 ++---
 net/ipv6/netfilter/nf_conntrack_reasm.c | 2 --
 net/ipv6/reassembly.c                   | 4 +---
 4 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
index 44f148a6bb57..1790b65944b3 100644
--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -411,7 +411,6 @@ int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 }
 
 #ifdef CONFIG_SYSCTL
-static long zero;
 
 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 	{
@@ -428,7 +427,6 @@ static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
-		.extra1		= &zero,
 		.extra2		= &init_net.ieee802154_lowpan.frags.high_thresh
 	},
 	{
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 5331a0d68374..d14d741fb05e 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -672,7 +672,7 @@ struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
 EXPORT_SYMBOL(ip_check_defrag);
 
 #ifdef CONFIG_SYSCTL
-static long zero;
+static int dist_min;
 
 static struct ctl_table ip4_frags_ns_ctl_table[] = {
 	{
@@ -689,7 +689,6 @@ static struct ctl_table ip4_frags_ns_ctl_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
-		.extra1		= &zero,
 		.extra2		= &init_net.ipv4.frags.high_thresh
 	},
 	{
@@ -705,7 +704,7 @@ static struct ctl_table ip4_frags_ns_ctl_table[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &zero
+		.extra1		= &dist_min,
 	},
 	{ }
 };
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index 6613f81e553a..a1dc0d6a5949 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -63,7 +63,6 @@ struct nf_ct_frag6_skb_cb
 static struct inet_frags nf_frags;
 
 #ifdef CONFIG_SYSCTL
-static long zero;
 
 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
 	{
@@ -79,7 +78,6 @@ static struct ctl_table nf_ct_frag6_sysctl_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
-		.extra1		= &zero,
 		.extra2		= &init_net.nf_frag.frags.high_thresh
 	},
 	{
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 2127da130dc2..e1c5fa5e3873 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -554,7 +554,6 @@ static const struct inet6_protocol frag_protocol = {
 };
 
 #ifdef CONFIG_SYSCTL
-static int zero;
 
 static struct ctl_table ip6_frags_ns_ctl_table[] = {
 	{
@@ -570,8 +569,7 @@ static struct ctl_table ip6_frags_ns_ctl_table[] = {
 		.data		= &init_net.ipv6.frags.low_thresh,
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &zero,
+		.proc_handler	= proc_doulongvec_minmax,
 		.extra2		= &init_net.ipv6.frags.high_thresh
 	},
 	{
-- 
2.18.0