Re: [PATCH] qemu-nbd: Fix a memleak in nbd_client_thread()

[Eric Blake]

On 12/1/20 12:13 AM, Alex Chen wrote:
> When the qio_channel_socket_connect_sync() fails
> we should goto 'out_socket' label to free the 'sioc' instead of
> goto 'out' label.
> In addition, now the 'out' label is useless, delete it.
> 
> Reported-by: Euler Robot <euler.robot@huawei.com>
> Signed-off-by: Alex Chen <alex.chen@huawei.com>
> ---
>  qemu-nbd.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 47587a709e..643b0777c0 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -275,7 +275,7 @@ static void *nbd_client_thread(void *arg)
>                                          saddr,
>                                          &local_error) < 0) {
>          error_report_err(local_error);
> -        goto out;
> +        goto out_socket;
>      }
>  
>      ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
> @@ -325,7 +325,6 @@ out_fd:
>      close(fd);
>  out_socket:
>      object_unref(OBJECT(sioc));
> -out:
>      g_free(info.name);
>      kill(getpid(), SIGTERM);
>      return (void *) EXIT_FAILURE;
> 

While the patch looks correct, we have a lot of duplication.  Simpler
might be a solution with only one exit label altogether:

diff --git i/qemu-nbd.c w/qemu-nbd.c
index a7075c5419d7..d7bdcd0011ba 100644
--- i/qemu-nbd.c
+++ w/qemu-nbd.c
@@ -265,8 +265,8 @@ static void *nbd_client_thread(void *arg)
     char *device = arg;
     NBDExportInfo info = { .request_sizes = false, .name = g_strdup("") };
     QIOChannelSocket *sioc;
-    int fd;
-    int ret;
+    int fd = -1;
+    int ret = EXIT_FAILURE;
     pthread_t show_parts_thread;
     Error *local_error = NULL;

@@ -278,26 +278,24 @@ static void *nbd_client_thread(void *arg)
         goto out;
     }

-    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
-                                NULL, NULL, NULL, &info, &local_error);
-    if (ret < 0) {
+    if (nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
+                              NULL, NULL, NULL, &info, &local_error) < 0) {
         if (local_error) {
             error_report_err(local_error);
         }
-        goto out_socket;
+        goto out;
     }

     fd = open(device, O_RDWR);
     if (fd < 0) {
         /* Linux-only, we can use %m in printf.  */
         error_report("Failed to open %s: %m", device);
-        goto out_socket;
+        goto out;
     }

-    ret = nbd_init(fd, sioc, &info, &local_error);
-    if (ret < 0) {
+    if (nbd_init(fd, sioc, &info, &local_error) < 0) {
         error_report_err(local_error);
-        goto out_fd;
+        goto out;
     }

     /* update partition table */
@@ -311,24 +309,18 @@ static void *nbd_client_thread(void *arg)
         dup2(STDOUT_FILENO, STDERR_FILENO);
     }

-    ret = nbd_client(fd);
-    if (ret) {
-        goto out_fd;
+    if (nbd_client(fd) == 0) {
+        ret = EXIT_SUCCESS;
     }
-    close(fd);
-    object_unref(OBJECT(sioc));
-    g_free(info.name);
-    kill(getpid(), SIGTERM);
-    return (void *) EXIT_SUCCESS;

-out_fd:
-    close(fd);
-out_socket:
+ out:
+    if (fd >= 0) {
+        close(fd);
+    }
     object_unref(OBJECT(sioc));
-out:
     g_free(info.name);
     kill(getpid(), SIGTERM);
-    return (void *) EXIT_FAILURE;
+    return (void *) (intptr_t) ret;
 }
 #endif /* HAVE_NBD_DEVICE */




-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org