netdev - [PATCH net-next] rhashtable: rhashtable_remove() must unlink in both tbl and future

lists.openwall.net		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: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 20 Jan 2015 16:58:26 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	davem@...emloft.net, Ying Xue <ying.xue@...driver.com>
Cc:	"richard.alpe@...csson.com >> Richard Alpe" 
	<richard.alpe@...csson.com>, Netdev <netdev@...r.kernel.org>,
	tipc-discussion@...ts.sourceforge.net
Subject: [PATCH net-next] rhashtable: rhashtable_remove() must unlink in both
 tbl and future_tbl

As removals can occur during resizes, entries may be referred to from
both tbl and future_tbl when the removal is requested. Therefore
rhashtable_remove() must unlink the entry in both tables if this is
the case. The existing code did search both tables but stopped when it
hit the first match.

Failing to do so resulted in use after remove.

Fixes: 97defe1 ("rhashtable: Per bucket locks & deferred expansion/shrinking")
Reported-by: Ying Xue <ying.xue@...driver.com>
Signed-off-by: Thomas Graf <tgraf@...g.ch>
---

Ying: This should fix the panic that was at the end of your TIPC
      related boot log. I'm still working on the use after free.

 lib/rhashtable.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index a4449c4..b1aa10e 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -592,6 +592,7 @@ bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
 	struct rhash_head *he;
 	spinlock_t *lock;
 	unsigned int hash;
+	bool ret = false;
 
 	rcu_read_lock();
 	tbl = rht_dereference_rcu(ht->tbl, ht);
@@ -609,17 +610,16 @@ restart:
 		}
 
 		rcu_assign_pointer(*pprev, obj->next);
-		atomic_dec(&ht->nelems);
-
-		spin_unlock_bh(lock);
-
-		rhashtable_wakeup_worker(ht);
-
-		rcu_read_unlock();
 
-		return true;
+		ret = true;
+		break;
 	}
 
+	/* The entry may be linked in either 'tbl', 'future_tbl', or both.
+	 * 'future_tbl' only exists for a short period of time during
+	 * resizing. Thus traversing both is fine and the added cost is
+	 * very rare.
+	 */
 	if (tbl != rht_dereference_rcu(ht->future_tbl, ht)) {
 		spin_unlock_bh(lock);
 
@@ -632,9 +632,15 @@ restart:
 	}
 
 	spin_unlock_bh(lock);
+
+	if (ret) {
+		atomic_dec(&ht->nelems);
+		rhashtable_wakeup_worker(ht);
+	}
+
 	rcu_read_unlock();
 
-	return false;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(rhashtable_remove);
 
-- 
1.9.3

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html