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rhashtable: Cap total number of entries to 2^31

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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>
This commit is contained in:
Herbert Xu
2017-04-27 13:44:51 +08:00
committed by David S. Miller
parent 4b726e81da
commit 6d684e5469
2 changed files with 8 additions and 2 deletions
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5
lib/rhashtable.c
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@@ -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)