[SRU][B][F][G][H][PATCH 1/1] netfilter: x_tables: fix compat match/target pad out-of-bound write

[Khalid Elmously]

From: Florian Westphal <fw at strlen.de>

BugLink: https://bugs.launchpad.net/bugs/1927682

xt_compat_match/target_from_user doesn't check that zeroing the area
to start of next rule won't write past end of allocated ruleset blob.

Remove this code and zero the entire blob beforehand.

Reported-by: syzbot+cfc0247ac173f597aaaa at syzkaller.appspotmail.com
Reported-by: Andy Nguyen <theflow at google.com>
Fixes: 9fa492cdc160c ("[NETFILTER]: x_tables: simplify compat API")
Signed-off-by: Florian Westphal <fw at strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(cherry picked from commit b29c457a6511435960115c0f548c4360d5f4801d)
Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
---
 net/ipv4/netfilter/arp_tables.c |  2 ++
 net/ipv4/netfilter/ip_tables.c  |  2 ++
 net/ipv6/netfilter/ip6_tables.c |  2 ++
 net/netfilter/x_tables.c        | 10 ++--------
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index e81eeb2389f92a..fc769df15c100b 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1230,6 +1230,8 @@ static int translate_compat_table(struct net *net,
 	if (!newinfo)
 		goto out_unlock;
 
+	memset(newinfo->entries, 0, size);
+
 	newinfo->number = compatr->num_entries;
 	for (i = 0; i < NF_ARP_NUMHOOKS; i++) {
 		newinfo->hook_entry[i] = compatr->hook_entry[i];
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index d5bd759a7ebaed..986d8538fb4ced 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1467,6 +1467,8 @@ translate_compat_table(struct net *net,
 	if (!newinfo)
 		goto out_unlock;
 
+	memset(newinfo->entries, 0, size);
+
 	newinfo->number = compatr->num_entries;
 	for (i = 0; i < NF_INET_NUMHOOKS; i++) {
 		newinfo->hook_entry[i] = compatr->hook_entry[i];
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 8e2985fc1ebc01..2cfce6eb98b43d 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1483,6 +1483,8 @@ translate_compat_table(struct net *net,
 	if (!newinfo)
 		goto out_unlock;
 
+	memset(newinfo->entries, 0, size);
+
 	newinfo->number = compatr->num_entries;
 	for (i = 0; i < NF_INET_NUMHOOKS; i++) {
 		newinfo->hook_entry[i] = compatr->hook_entry[i];
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 4638d42a22e405..d40acfce300764 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -636,7 +636,7 @@ void xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
 {
 	const struct xt_match *match = m->u.kernel.match;
 	struct compat_xt_entry_match *cm = (struct compat_xt_entry_match *)m;
-	int pad, off = xt_compat_match_offset(match);
+	int off = xt_compat_match_offset(match);
 	u_int16_t msize = cm->u.user.match_size;
 	char name[sizeof(m->u.user.name)];
 
@@ -646,9 +646,6 @@ void xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
 		match->compat_from_user(m->data, cm->data);
 	else
 		memcpy(m->data, cm->data, msize - sizeof(*cm));
-	pad = XT_ALIGN(match->matchsize) - match->matchsize;
-	if (pad > 0)
-		memset(m->data + match->matchsize, 0, pad);
 
 	msize += off;
 	m->u.user.match_size = msize;
@@ -991,7 +988,7 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
 {
 	const struct xt_target *target = t->u.kernel.target;
 	struct compat_xt_entry_target *ct = (struct compat_xt_entry_target *)t;
-	int pad, off = xt_compat_target_offset(target);
+	int off = xt_compat_target_offset(target);
 	u_int16_t tsize = ct->u.user.target_size;
 	char name[sizeof(t->u.user.name)];
 
@@ -1001,9 +998,6 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
 		target->compat_from_user(t->data, ct->data);
 	else
 		memcpy(t->data, ct->data, tsize - sizeof(*ct));
-	pad = XT_ALIGN(target->targetsize) - target->targetsize;
-	if (pad > 0)
-		memset(t->data + target->targetsize, 0, pad);
 
 	tsize += off;
 	t->u.user.target_size = tsize;
-- 
2.17.1