[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 <zhengbi...@huawei.com>
---

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