ebtables doesn't include the base chain policies in the rule count,
so we need to add them manually when we call into the x_tables core
to allocate space for the comapt offset table.
This lead syzbot to trigger:
WARNING: CPU: 1 PID: 9012 at net/netfilter/x_tables.c:649
xt_compat_add_offset.cold+0x11/0x36 net/netfilter/x_tables.c:649
Reported-by: syzbot+276ddebab3382bbf72db@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 2035f3ff8eaa ("netfilter: ebtables: compat: un-break 32bit setsockopt when no rules are present")
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
net/bridge/netfilter/ebtables.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index fd84b48e48b5..c8177a89f52c 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1770,20 +1770,28 @@ static int compat_calc_entry(const struct ebt_entry *e,
return 0;
}
+static int ebt_compat_init_offsets(unsigned int number)
+{
+ if (number > INT_MAX)
+ return -EINVAL;
+
+ /* also count the base chain policies */
+ number += NF_BR_NUMHOOKS;
+
+ return xt_compat_init_offsets(NFPROTO_BRIDGE, number);
+}
static int compat_table_info(const struct ebt_table_info *info,
struct compat_ebt_replace *newinfo)
{
unsigned int size = info->entries_size;
const void *entries = info->entries;
+ int ret;
newinfo->entries_size = size;
- if (info->nentries) {
- int ret = xt_compat_init_offsets(NFPROTO_BRIDGE,
- info->nentries);
- if (ret)
- return ret;
- }
+ ret = ebt_compat_init_offsets(info->nentries);
+ if (ret)
+ return ret;
return EBT_ENTRY_ITERATE(entries, size, compat_calc_entry, info,
entries, newinfo);
@@ -2234,11 +2242,9 @@ static int compat_do_replace(struct net *net, void __user *user,
xt_compat_lock(NFPROTO_BRIDGE);
- if (tmp.nentries) {
- ret = xt_compat_init_offsets(NFPROTO_BRIDGE, tmp.nentries);
- if (ret < 0)
- goto out_unlock;
- }
+ ret = ebt_compat_init_offsets(tmp.nentries);
+ if (ret < 0)
+ goto out_unlock;
ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state);
if (ret < 0)
--
2.21.0
