netdev - [PATCH net-next] net-sysfs: remove possible sleep from an RCU read-side critical section

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Date:   Mon, 22 Mar 2021 16:43:29 +0100
From:   Antoine Tenart <atenart@...nel.org>
To:     davem@...emloft.net, kuba@...nel.org, alexander.duyck@...il.com
Cc:     Antoine Tenart <atenart@...nel.org>, netdev@...r.kernel.org,
        kernel test robot <oliver.sang@...el.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH net-next] net-sysfs: remove possible sleep from an RCU read-side critical section

xps_queue_show is mostly made of an RCU read-side critical section and
calls bitmap_zalloc with GFP_KERNEL in the middle of it. That is not
allowed as this call may sleep and such behaviours aren't allowed in RCU
read-side critical sections. Fix this by using GFP_NOWAIT instead.

Fixes: 5478fcd0f483 ("net: embed nr_ids in the xps maps")
Reported-by: kernel test robot <oliver.sang@...el.com>
Suggested-by: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Antoine Tenart <atenart@...nel.org>
---

Fix sent to net-next as it fixes an issue only in net-next.

 net/core/net-sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 562a42fcd437..f6197774048b 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1378,7 +1378,7 @@ static ssize_t xps_queue_show(struct net_device *dev, unsigned int index,
 	nr_ids = dev_maps ? dev_maps->nr_ids :
 		 (type == XPS_CPUS ? nr_cpu_ids : dev->num_rx_queues);
 
-	mask = bitmap_zalloc(nr_ids, GFP_KERNEL);
+	mask = bitmap_zalloc(nr_ids, GFP_NOWAIT);
 	if (!mask) {
 		rcu_read_unlock();
 		return -ENOMEM;
-- 
2.30.2