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authorHerbert Xu <herbert@gondor.apana.org.au>2017-04-27 13:44:51 +0800
committerDavid S. Miller <davem@davemloft.net>2017-04-27 11:48:24 -0400
commit6d684e54690caef45cf14051ddeb7c71beeb681b (patch)
tree1544faf80a19bf2fa47d9f2a1e5f2f98dbb17545 /lib
parent4b726e81dab2cefefd2c1cb00e3074ac0eec4b15 (diff)
rhashtable: Cap total number of entries to 2^31
When max_size is not set or if it set to a sufficiently large value, the nelems counter can overflow. This would cause havoc with the automatic shrinking as it would then attempt to fit a huge number of entries into a tiny hash table. This patch fixes this by adding max_elems to struct rhashtable to cap the number of elements. This is set to 2^31 as nelems is not a precise count. This is sufficiently smaller than UINT_MAX that it should be safe. When max_size is set max_elems will be lowered to at most twice max_size as is the status quo. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
-rw-r--r--lib/rhashtable.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index f3b82e0d417b..751630bbe409 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -961,6 +961,11 @@ int rhashtable_init(struct rhashtable *ht,
if (params->max_size)
ht->p.max_size = rounddown_pow_of_two(params->max_size);
+ /* Cap total entries at 2^31 to avoid nelems overflow. */
+ ht->max_elems = 1u << 31;
+ if (ht->p.max_size < ht->max_elems / 2)
+ ht->max_elems = ht->p.max_size * 2;
+
ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
if (params->nelem_hint)

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