[4.2.y-ckt stable] Patch "rhashtable: Enforce minimum size on initial hash table" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    rhashtable: Enforce minimum size on initial hash table

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 2cafdad85024243cb90651fb652f8fed75dc294f Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert at gondor.apana.org.au>
Date: Wed, 16 Dec 2015 18:13:14 +0800
Subject: rhashtable: Enforce minimum size on initial hash table

[ Upstream commit 3a324606bbabfc30084ce9d08169910773ba9a92 ]

William Hua <william.hua at 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 at canonical.com>
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 lib/rhashtable.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index cc0c697..7d79983 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -726,9 +726,6 @@ 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);
@@ -748,6 +745,9 @@ 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
--
1.9.1