[PATCH v4 2/2] block/nbd: fix memory leak in nbd_open()

[pannengyuan]

From: Pan Nengyuan <address@hidden>

In currently implementation there will be a memory leak when
nbd_client_connect() returns error status. Here is an easy way to
reproduce:

1. run qemu-iotests as follow and check the result with asan:
    ./check -raw 143

Following is the asan output backtrack:
Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7f629688a560 in calloc (/usr/lib64/libasan.so.3+0xc7560)
    #1 0x7f6295e7e015 in g_malloc0  (/usr/lib64/libglib-2.0.so.0+0x50015)
    #2 0x56281dab4642 in qobject_input_start_struct  
/mnt/sdb/qemu-4.2.0-rc0/qapi/qobject-input-visitor.c:295
    #3 0x56281dab1a04 in visit_start_struct  
/mnt/sdb/qemu-4.2.0-rc0/qapi/qapi-visit-core.c:49
    #4 0x56281dad1827 in visit_type_SocketAddress  qapi/qapi-visit-sockets.c:386
    #5 0x56281da8062f in nbd_config   /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1716
    #6 0x56281da8062f in nbd_process_options 
/mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1829
    #7 0x56281da8062f in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873

Direct leak of 15 byte(s) in 1 object(s) allocated from:
    #0 0x7f629688a3a0 in malloc (/usr/lib64/libasan.so.3+0xc73a0)
    #1 0x7f6295e7dfbd in g_malloc (/usr/lib64/libglib-2.0.so.0+0x4ffbd)
    #2 0x7f6295e96ace in g_strdup (/usr/lib64/libglib-2.0.so.0+0x68ace)
    #3 0x56281da804ac in nbd_process_options 
/mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1834
    #4 0x56281da804ac in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873

Indirect leak of 24 byte(s) in 1 object(s) allocated from:
    #0 0x7f629688a3a0 in malloc (/usr/lib64/libasan.so.3+0xc73a0)
    #1 0x7f6295e7dfbd in g_malloc (/usr/lib64/libglib-2.0.so.0+0x4ffbd)
    #2 0x7f6295e96ace in g_strdup (/usr/lib64/libglib-2.0.so.0+0x68ace)
    #3 0x56281dab41a3 in qobject_input_type_str_keyval 
/mnt/sdb/qemu-4.2.0-rc0/qapi/qobject-input-visitor.c:536
    #4 0x56281dab2ee9 in visit_type_str 
/mnt/sdb/qemu-4.2.0-rc0/qapi/qapi-visit-core.c:297
    #5 0x56281dad0fa1 in visit_type_UnixSocketAddress_members 
qapi/qapi-visit-sockets.c:141
    #6 0x56281dad17b6 in visit_type_SocketAddress_members 
qapi/qapi-visit-sockets.c:366
    #7 0x56281dad186a in visit_type_SocketAddress qapi/qapi-visit-sockets.c:393
    #8 0x56281da8062f in nbd_config /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1716
    #9 0x56281da8062f in nbd_process_options 
/mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1829
    #10 0x56281da8062f in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873

Fixes: 8f071c9db506e03ab
Reported-by: Euler Robot <address@hidden>
Signed-off-by: Pan Nengyuan <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Cc: qemu-stable <address@hidden>
Cc: Vladimir Sementsov-Ogievskiy <address@hidden>
---
Changes v2 to v1:
- add a new function to do the common cleanups (suggested by Stefano
  Garzarella).
---
Changes v3 to v2:
- split in two patches(suggested by Stefano Garzarella)
---
Changes v4 to v3:
- replace function name from nbd_free_bdrvstate_prop to
  nbd_clear_bdrvstate and add Fixes tag.
---
 block/nbd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/nbd.c b/block/nbd.c
index 8b4a65a..9062409 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1891,6 +1891,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, 
int flags,
 
     ret = nbd_client_connect(bs, errp);
     if (ret < 0) {
+        nbd_clear_bdrvstate(s);
         return ret;
     }
     /* successfully connected */
-- 
2.7.2.windows.1