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hash: fix race condition in iterate

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In rte_hash_iterate, the reader lock did not protect the
while loop which checks empty entry. This created a race
condition that the entry may become empty when enters
the lock, then a wrong key data value would be read out.

This commit reads out the position in the while condition,
which makes sure that the position will not be changed
to empty before entering the lock.

Fixes: f2e3001b53ec ("hash: support read/write concurrency")
Cc: stable@dpdk.org

Reported-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Acked-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
This commit is contained in:
Yipeng Wang 2018-10-22 11:39:45 -07:00 committed by Thomas Monjalon
parent 86c1ef2090
commit 9904094344
1 changed files with 2 additions and 3 deletions
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5
lib/librte_hash/rte_cuckoo_hash.c
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@ -1318,7 +1318,7 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32
idx = *next % RTE_HASH_BUCKET_ENTRIES;
/* If current position is empty, go to the next one */
while (h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) {
while ((position = h->buckets[bucket_idx].key_idx[idx]) == EMPTY_SLOT) {
(*next)++;
/* End of table */
if (*next == total_entries)
@ -1326,9 +1326,8 @@ 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);
/* 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 +
position * h->key_entry_size);
/* Return key and data */