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netfilter: x_tables: fix compat match/target pad out-of-bound write

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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: 9fa492cdc1 ("[NETFILTER]: x_tables: simplify compat API")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2021-04-07 21:38:57 +02:00 committed by Pablo Neira Ayuso
parent d163a925eb
commit b29c457a65
4 changed files with 8 additions and 8 deletions
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2
net/ipv4/netfilter/arp_tables.c
View File

@ -1193,6 +1193,8 @@ 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];

2
net/ipv4/netfilter/ip_tables.c
View File

@ -1428,6 +1428,8 @@ 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];

2
net/ipv6/netfilter/ip6_tables.c
View File

@ -1443,6 +1443,8 @@ 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];

10
net/netfilter/x_tables.c
View File

@ -733,7 +733,7 @@ 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)];
@ -743,9 +743,6 @@ 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;
@ -1116,7 +1113,7 @@ 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)];
@ -1126,9 +1123,6 @@ 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;