nbd: Fix memory leak in nbd_add_socket

When adding first socket to nbd, if nsock's allocation failed, the data
structure member "config->socks" was reallocated, but the data structure
member "config->num_connections" was not updated. A memory leak will occur
then because the function "nbd_config_put" will free "config->socks" only
when "config->num_connections" is not zero.

Fixes: 03bf73c315ed ("nbd: prevent memory leak")
Reported-by: syzbot+934037347002901b8d2a@syzkaller.appspotmail.com
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 43cff01a5a675d47cd9bcb60ffcf1440ac8fc871..ce7e9f223b20b821e2760f955f6df5bfec8f853e 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1033,25 +1033,26 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
             test_bit(NBD_RT_BOUND, &config->runtime_flags))) {
                dev_err(disk_to_dev(nbd->disk),
                        "Device being setup by another task");
-               sockfd_put(sock);
-               return -EBUSY;
+               err = -EBUSY;
+               goto put_socket;
+       }
+
+       nsock = kzalloc(sizeof(*nsock), GFP_KERNEL);
+       if (!nsock) {
+               err = -ENOMEM;
+               goto put_socket;
        }
 
        socks = krealloc(config->socks, (config->num_connections + 1) *
                         sizeof(struct nbd_sock *), GFP_KERNEL);
        if (!socks) {
-               sockfd_put(sock);
-               return -ENOMEM;
+               kfree(nsock);
+               err = -ENOMEM;
+               goto put_socket;
        }
 
        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);
@@ -1063,6 +1064,10 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
        atomic_inc(&config->live_connections);
 
        return 0;
+
+put_socket:
+       sockfd_put(sock);
+       return err;
 }
 
 static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)