lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [day] [month] [year] [list]
Date:   Wed, 24 Apr 2019 10:46:39 -0400
From:   Sasha Levin <>
Cc:     Sven Eckelmann <>,
        Simon Wunderlich <>,
        Sasha Levin <>,
Subject: [PATCH AUTOSEL 4.14 05/35] batman-adv: Reduce tt_local hash refcnt only for removed entry

From: Sven Eckelmann <>

[ Upstream commit 3d65b9accab4a7ed5038f6df403fbd5e298398c7 ]

The batadv_hash_remove is a function which searches the hashtable for an
entry using a needle, a hashtable bucket selection function and a compare
function. It will lock the bucket list and delete an entry when the compare
function matches it with the needle. It returns the pointer to the
hlist_node which matches or NULL when no entry matches the needle.

The batadv_tt_local_remove is not itself protected in anyway to avoid that
any other function is modifying the hashtable between the search for the
entry and the call to batadv_hash_remove. It can therefore happen that the
entry either doesn't exist anymore or an entry was deleted which is not the
same object as the needle. In such an situation, the reference counter (for
the reference stored in the hashtable) must not be reduced for the needle.
Instead the reference counter of the actually removed entry has to be

Otherwise the reference counter will underflow and the object might be
freed before all its references were dropped. The kref helpers reported
this problem as:

  refcount_t: underflow; use-after-free.

Fixes: ef72706a0543 ("batman-adv: protect tt_local_entry from concurrent delete events")
Signed-off-by: Sven Eckelmann <>
Signed-off-by: Simon Wunderlich <>
Signed-off-by: Sasha Levin <>
 net/batman-adv/translation-table.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 9da3455847ff..6c3e446abeed 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1313,9 +1313,10 @@ u16 batadv_tt_local_remove(struct batadv_priv *bat_priv, const u8 *addr,
 			   unsigned short vid, const char *message,
 			   bool roaming)
+	struct batadv_tt_local_entry *tt_removed_entry;
 	struct batadv_tt_local_entry *tt_local_entry;
 	u16 flags, curr_flags = BATADV_NO_FLAGS;
-	void *tt_entry_exists;
+	struct hlist_node *tt_removed_node;
 	tt_local_entry = batadv_tt_local_hash_find(bat_priv, addr, vid);
 	if (!tt_local_entry)
@@ -1344,15 +1345,18 @@ u16 batadv_tt_local_remove(struct batadv_priv *bat_priv, const u8 *addr,
 	batadv_tt_local_event(bat_priv, tt_local_entry, BATADV_TT_CLIENT_DEL);
-	tt_entry_exists = batadv_hash_remove(bat_priv->tt.local_hash,
+	tt_removed_node = batadv_hash_remove(bat_priv->tt.local_hash,
-	if (!tt_entry_exists)
+	if (!tt_removed_node)
 		goto out;
-	/* extra call to free the local tt entry */
-	batadv_tt_local_entry_put(tt_local_entry);
+	/* drop reference of remove hash entry */
+	tt_removed_entry = hlist_entry(tt_removed_node,
+				       struct batadv_tt_local_entry,
+				       common.hash_entry);
+	batadv_tt_local_entry_put(tt_removed_entry);
 	if (tt_local_entry)

Powered by blists - more mailing lists