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: a998f712f77e ("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>

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 2ff7ed91663ae4fd105c24ad98454a51c329cf86..a98e71db7dd21d9fc76d9a87460059e0d6d5beb8 100644 (file)
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -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