[PATCH v2] nbd: Fix memory leak in nbd_add_socket

[Zheng Bin]

If we add first socket to nbd, config->socks is malloced but
num_connections does not update(nsock's allocation fail), the memory
is leaked. Cause in later nbd_config_put(), will only free config->socks
when num_connections is not 0.

Let nsock's allocation first to avoid this.

Fixes: 03bf73c315ed ("nbd: prevent memory leak")
Signed-off-by: Zheng Bin <zhengbin13@xxxxxxxxxx>
---

v1->v2: modify comments

 drivers/block/nbd.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 43cff01a5a67..3e7709317b17 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1037,21 +1037,22 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 		return -EBUSY;
 	}

+	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
+	if (!nsock) {
+		sockfd_put(sock);
+		return -ENOMEM;
+	}
+
 	socks = krealloc(config->socks, (config->num_connections + 1) *
 			 sizeof(struct nbd_sock *), GFP_KERNEL);
 	if (!socks) {
 		sockfd_put(sock);
+		kfree(nsock);
 		return -ENOMEM;
 	}

 	config->socks = socks;

-	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
-	if (!nsock) {
-		sockfd_put(sock);
-		return -ENOMEM;
-	}
-
 	nsock->fallback_index = -1;
 	nsock->dead = false;
 	mutex_init(&nsock->tx_lock);
--
2.26.0.106.g9fadedd