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batman-adv: Avoid race in TT TVLV allocator helper

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commit 8ba0f9bd3b upstream.

The functions batadv_tt_prepare_tvlv_local_data and
batadv_tt_prepare_tvlv_global_data are responsible for preparing a buffer
which can be used to store the TVLV container for TT and add the VLAN
information to it.

This will be done in three phases:

1. count the number of VLANs and their entries
2. allocate the buffer using the counters from the previous step and limits
   from the caller (parameter tt_len)
3. insert the VLAN information to the buffer

The step 1 and 3 operate on a list which contains the VLANs. The access to
these lists must be protected with an appropriate lock or otherwise they
might operate on on different entries. This could for example happen when
another context is adding VLAN entries to this list.

This could lead to a buffer overflow in these functions when enough entries
were added between step 1 and 3 to the VLAN lists that the buffer room for
the entries (*tt_change) is smaller then the now required extra buffer for
new VLAN entries.

Fixes: 7ea7b4a142 ("batman-adv: make the TT CRC logic VLAN specific")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Eckelmann
2020-03-16 23:30:54 +01:00
committed by Greg Kroah-Hartman
parent 8142ea6bab
commit f4d59337e0
1 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
net/batman-adv/translation-table.c
View File

@@ -867,7 +867,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
struct batadv_orig_node_vlan *vlan;
u8 *tt_change_ptr;
rcu_read_lock();
spin_lock_bh(&orig_node->vlan_list_lock);
hlist_for_each_entry_rcu(vlan, &orig_node->vlan_list, list) {
num_vlan++;
num_entries += atomic_read(&vlan->tt.num_entries);
@@ -905,7 +905,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
*tt_change = (struct batadv_tvlv_tt_change *)tt_change_ptr;
out:
rcu_read_unlock();
spin_unlock_bh(&orig_node->vlan_list_lock);
return tvlv_len;
}
@@ -941,7 +941,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
u8 *tt_change_ptr;
int change_offset;
rcu_read_lock();
spin_lock_bh(&bat_priv->softif_vlan_list_lock);
hlist_for_each_entry_rcu(vlan, &bat_priv->softif_vlan_list, list) {
num_vlan++;
num_entries += atomic_read(&vlan->tt.num_entries);
@@ -979,7 +979,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
*tt_change = (struct batadv_tvlv_tt_change *)tt_change_ptr;
out:
rcu_read_unlock();
spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
return tvlv_len;
}