[PATCH 4.14 66/68] netfilter: x_tables: fix compat match/target pad out-of-bound write

Greg Kroah-Hartman
2021-04-15T15:09:52Z

From: Florian Westphal <fw@strlen.de>

commit b29c457a6511435960115c0f548c4360d5f4801d upstream.

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@syzkaller.appspotmail.com
Reported-by: Andy Nguyen <theflow@google.com>
Fixes: 9fa492cdc160c ("[NETFILTER]: x_tables: simplify compat API")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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(-)

--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1196,6 +1196,8 @@ static int translate_compat_table(struct
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];
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1432,6 +1432,8 @@ 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];
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1449,6 +1449,8 @@ 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];
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -638,7 +638,7 @@ void xt_compat_match_from_user(struct xt
{
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)];

@@ -648,9 +648,6 @@ void xt_compat_match_from_user(struct xt
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;
@@ -993,7 +990,7 @@ void xt_compat_target_from_user(struct x
{
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)];

@@ -1003,9 +1000,6 @@ void xt_compat_target_from_user(struct x
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;