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>
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index f3b82e0..751630b 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -961,6 +961,11 @@
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)