diff mbox series

[4/5] batman-adv: Prevent duplicated global TT entry

Message ID 20180812190445.28013-5-sven@narfation.org (mailing list archive)
State Superseded, archived
Delegated to: Simon Wunderlich
Headers
Series batman-adv: Missing list checks for *list_add* |

Commit Message

Sven Eckelmann Aug. 12, 2018, 7:04 p.m. UTC 
  The function batadv_tt_global_orig_entry_add is responsible for adding new
tt_orig_list_entry to the orig_list. It first checks whether the entry
already is in the list or not. If it is, then the creation of a new entry
is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: c5eb5bb30321 ("batman-adv: add reference counting for type batadv_tt_orig_list_entry")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/translation-table.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Marek Lindner Sept. 6, 2018, 12:03 p.m. UTC | #1 
On Monday, 13 August 2018 03:04:44 HKT Sven Eckelmann wrote:
> The function batadv_tt_global_orig_entry_add is responsible for adding new
> tt_orig_list_entry to the orig_list. It first checks whether the entry
> already is in the list or not. If it is, then the creation of a new entry
> is aborted.
> 
> But the lock for the list is only held when the list is really modified.
> This could lead to duplicated entries because another context could create
> an entry with the same key between the check and the list manipulation.
> 
> The check and the manipulation of the list must therefore be in the same
> locked code section.
> 
> Fixes: c5eb5bb30321 ("batman-adv: add reference counting for type
> batadv_tt_orig_list_entry") Signed-off-by: Sven Eckelmann
> <sven@narfation.org>


Acked-by: Marek Lindner <mareklindner@neomailbox.ch>

Cheers,
Marek
diff mbox series

Patch

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 12a2b7d2..d21624c4 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1613,6 +1613,8 @@  batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 {
 	struct batadv_tt_orig_list_entry *orig_entry;
 
+	spin_lock_bh(&tt_global->list_lock);
+
 	orig_entry = batadv_tt_global_orig_entry_find(tt_global, orig_node);
 	if (orig_entry) {
 		/* refresh the ttvn: the current value could be a bogus one that
@@ -1635,11 +1637,9 @@  batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 	orig_entry->flags = flags;
 	kref_init(&orig_entry->refcount);
 
-	spin_lock_bh(&tt_global->list_lock);
 	kref_get(&orig_entry->refcount);
 	hlist_add_head_rcu(&orig_entry->list,
 			   &tt_global->orig_list);
-	spin_unlock_bh(&tt_global->list_lock);
 	atomic_inc(&tt_global->orig_list_count);
 
 sync_flags:
@@ -1647,6 +1647,8 @@  batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 out:
 	if (orig_entry)
 		batadv_tt_orig_list_entry_put(orig_entry);
+
+	spin_unlock_bh(&tt_global->list_lock);
 }
 
 /**