Commit 3a324606 authored Dec 16, 2015 by Herbert Xu Committed by David S. Miller Dec 16, 2015

rhashtable: Enforce minimum size on initial hash table

William Hua <william.hua@canonical.com> wrote:
>
> I wasn't aware there was an enforced minimum size. I simply set the
> nelem_hint in the rhastable_params struct to 1, expecting it to grow as
> needed. This caused a segfault afterwards when trying to insert an
> element.

OK we're doing the size computation before we enforce the limit
on min_size.

---8<---
We need to do the initial hash table size computation after we
have obtained the correct min_size/max_size parameters.  Otherwise
we may end up with a hash table whose size is outside the allowed
envelope.

Fixes: a998f712 ("rhashtable: Round up/down min/max_size to...")
Reported-by: William Hua <william.hua@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 887dc9f2

lib/rhashtable.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -738,9 +738,6 @@ int rhashtable_init(struct rhashtable *ht,
		if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
		return -EINVAL;

		if (params->nelem_hint)
		size = rounded_hashtable_size(params);

		memset(ht, 0, sizeof(*ht));
		mutex_init(&ht->mutex);
		spin_lock_init(&ht->lock);
		@@ -760,6 +757,9 @@ int rhashtable_init(struct rhashtable *ht,

		ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);

		if (params->nelem_hint)
		size = rounded_hashtable_size(&ht->p);

		/* The maximum (not average) chain length grows with the
		* size of the hash table, at a rate of (log N)/(log log N).
		* The value of 16 is selected so that even if the hash