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From: Qiaobin Fu <qiaobinf@bu.edu>
To: bruce.richardson@intel.com, pablo.de.lara.guarch@intel.com
Cc: dev@dpdk.org, doucette@bu.edu, keith.wiles@intel.com,
	sameh.gobriel@intel.com, charlie.tai@intel.com,
	stephen@networkplumber.org, nd@arm.com,
	honnappa.nagarahalli@arm.com, yipeng1.wang@intel.com,
	michel@digirati.com.br, qiaobinf@bu.edu
Subject: [dpdk-dev] [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate()
Date: Tue,  9 Oct 2018 19:29:06 +0000
Message-ID: <20181009192907.85650-1-qiaobinf@bu.edu> (raw)
In-Reply-To: <20180831165101.20026-1-qiaobinf@bu.edu>

In current implementation of rte_hash_iterate(), it
tries to obtain the lock after the while loop. However,
this may lead to a bug. Notice the following racing condition:

1. The while loop above finishes because it finds
   a not empty slot. But it does so without a lock.
2. Then we get the lock.
3. The position that was once not empty is now empty.
   BUG because next_key is invalid.

This patch fixes this small bug.

Signed-off-by: Qiaobin Fu <qiaobinf@bu.edu>
Reviewed-by: Michel Machado <michel@digirati.com.br>
---
 lib/librte_hash/rte_cuckoo_hash.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index f7b86c8c9..a3e76684d 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -1317,16 +1317,18 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32
 	bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
 	idx = *next % RTE_HASH_BUCKET_ENTRIES;
 
+	__hash_rw_reader_lock(h);
 	/* If current position is empty, go to the next one */
 	while (h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) {
 		(*next)++;
 		/* End of table */
-		if (*next == total_entries)
+		if (*next == total_entries) {
+			__hash_rw_reader_unlock(h);
 			return -ENOENT;
+		}
 		bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
 		idx = *next % RTE_HASH_BUCKET_ENTRIES;
 	}
-	__hash_rw_reader_lock(h);
 	/* Get position of entry in key table */
 	position = h->buckets[bucket_idx].key_idx[idx];
 	next_key = (struct rte_hash_key *) ((char *)h->key_store +
-- 
2.17.1

  parent reply	other threads:[~2018-10-09 19:30 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-31 16:51 [dpdk-dev] [PATCH v3] hash table: add an iterator over conflicting entries Qiaobin Fu
2018-08-31 22:53 ` Gaëtan Rivet
2018-09-04 18:46   ` Michel Machado
2018-09-02 22:05 ` Honnappa Nagarahalli
2018-09-04 19:36   ` Michel Machado
2018-09-05 22:13     ` Honnappa Nagarahalli
2018-09-06 14:28       ` Michel Machado
2018-09-12 20:37         ` Honnappa Nagarahalli
2018-09-20 19:50           ` Michel Machado
2018-09-04 18:55 ` Wang, Yipeng1
2018-09-04 19:07   ` Michel Machado
2018-09-04 19:51     ` Wang, Yipeng1
2018-09-04 20:26       ` Michel Machado
2018-09-04 20:57         ` Wang, Yipeng1
2018-09-05 17:52           ` Michel Machado
2018-09-05 20:27             ` Wang, Yipeng1
2018-09-06 13:34               ` Michel Machado
2018-10-09 19:29 ` Qiaobin Fu [this message]
2018-10-09 19:29   ` [dpdk-dev] [PATCH v4 2/2] " Qiaobin Fu
2018-10-10  2:54     ` Wang, Yipeng1
2018-10-10  1:55   ` [dpdk-dev] [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate() Wang, Yipeng1

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