netdev - Re: [PATCH v2] rps: fix insufficient bounds checking in store_rps_dev_flow_table

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Message-ID: <1324645592.2223.9.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Fri, 23 Dec 2011 14:06:32 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Xi Wang <xi.wang@...il.com>
Cc:	Tom Herbert <therbert@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] rps: fix insufficient bounds checking in
 store_rps_dev_flow_table_cnt()

Le vendredi 23 décembre 2011 à 00:56 -0500, Xi Wang a écrit :
> On Dec 23, 2011, at 12:35 AM, Eric Dumazet wrote:
> > By the way, the theorical limit on number of flows on 64bit platform is
> > 2^32  (rxhash being an u32)
> > 
> > Not sure spending 32GB per table would be wise for typical machines :)
> 
> True, a large rps_flow_cnt is not that useful. ;-)
> 
> Anyway, my point is that if the patch looks confusing to you, then
> it is probably not good.  I am happy to see a more elegant fix.
> 

I'll submit following patch for net-next, once your patch is in this
tree.

- Full u32 range on 64bit arches (2^32 flows max)
- Use of kstrtoul() instead of simple_strtoul()

 net/core/net-sysfs.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 385aefe..63bd152 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -618,7 +618,7 @@ static ssize_t show_rps_dev_flow_table_cnt(struct netdev_rx_queue *queue,
 					   char *buf)
 {
 	struct rps_dev_flow_table *flow_table;
-	unsigned int val = 0;
+	unsigned long val = 0;
 
 	rcu_read_lock();
 	flow_table = rcu_dereference(queue->rps_flow_table);
@@ -626,7 +626,7 @@ static ssize_t show_rps_dev_flow_table_cnt(struct netdev_rx_queue *queue,
 		val = flow_table->mask + 1;
 	rcu_read_unlock();
 
-	return sprintf(buf, "%u\n", val);
+	return sprintf(buf, "%lu\n", val);
 }
 
 static void rps_dev_flow_table_release_work(struct work_struct *work)
@@ -650,24 +650,23 @@ static ssize_t store_rps_dev_flow_table_cnt(struct netdev_rx_queue *queue,
 				     struct rx_queue_attribute *attr,
 				     const char *buf, size_t len)
 {
-	unsigned int count;
-	char *endp;
+	unsigned long i, count;
 	struct rps_dev_flow_table *table, *old_table;
 	static DEFINE_SPINLOCK(rps_dev_flow_lock);
+	int rc;
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
-	count = simple_strtoul(buf, &endp, 0);
-	if (endp == buf)
-		return -EINVAL;
+	rc = kstrtoul(buf, 0, &count);
+	if (rc < 0)
+		return rc;
 
 	if (count) {
-		int i;
-
-		if (count > INT_MAX)
-			return -EINVAL;
 		count = roundup_pow_of_two(count);
+		if (!count ||
+		    count != (unsigned long)(u32)count)
+			return -EINVAL;
 		if (count > (ULONG_MAX - sizeof(struct rps_dev_flow_table))
 				/ sizeof(struct rps_dev_flow)) {
 			/* Enforce a limit to prevent overflow */


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