[PATCH 4.19 10/13] netfilter: x_tables: fix compat match/target pad out-of-bound write

[Greg Kroah-Hartman]

From: Florian Westphal <f...@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+cfc0247ac173f597a...@syzkaller.appspotmail.com
Reported-by: Andy Nguyen <thef...@google.com>
Fixes: 9fa492cdc160c ("[NETFILTER]: x_tables: simplify compat API")
Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -1195,6 +1195,8 @@ 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
@@ -1433,6 +1433,8 @@ 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
@@ -1448,6 +1448,8 @@ 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
@@ -738,7 +738,7 @@ 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)];
 
@@ -748,9 +748,6 @@ 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;
@@ -1121,7 +1118,7 @@ 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)];
 
@@ -1131,9 +1128,6 @@ 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;