linux-kernel - [PATCH AUTOSEL 4.9 06/23] batman-adv: Prevent duplicated global TT entry

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Message-Id: <20181008152703.70891-6-sashal@kernel.org>
Date:   Mon,  8 Oct 2018 11:26:46 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Sven Eckelmann <sven@...fation.org>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.9 06/23] batman-adv: Prevent duplicated global TT entry

From: Sven Eckelmann <sven@...fation.org>

[ Upstream commit e7136e48ffdfb9f37b0820f619380485eb407361 ]

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: d657e621a0f5 ("batman-adv: add reference counting for type batadv_tt_orig_list_entry")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 net/batman-adv/translation-table.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 0dc85eb1cb7a..b9f9a310eb78 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1550,6 +1550,8 @@ 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
@@ -1570,16 +1572,16 @@ batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 	orig_entry->ttvn = ttvn;
 	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);
 
 out:
 	if (orig_entry)
 		batadv_tt_orig_list_entry_put(orig_entry);
+
+	spin_unlock_bh(&tt_global->list_lock);
 }
 
 /**
-- 
2.17.1