[PATCH] backup-top: fix a memory leak in bdrv_backup_top_append()

[pannengyuan]

From: Pan Nengyuan <address@hidden>

top->opaque is aleardy malloced in bdrv_new_open_driver(), and then change
the pointer but without freeing it. It will cause a memory leak, the leak
stack is as follow:

Direct leak of 24 byte(s) in 1 object(s) allocated from:
  #0 0x7ff6f7be4970 (/lib64/libasan.so.5+0xef970)  ??:?
  #1 0x7ff6f723849d (/lib64/libglib-2.0.so.0+0x5249d)  ??:?
  #2 0x564c0d44caae (./x86_64-softmmu/qemu-system-x86_64+0x3b40aae)  
/mnt/sdb/qemu/block.c:1289
  #3 0x564c0d44dbaf (./x86_64-softmmu/qemu-system-x86_64+0x3b41baf)  
/mnt/sdb/qemu/block.c:1359
  #4 0x564c0d71618f (./x86_64-softmmu/qemu-system-x86_64+0x3e0a18f)  
/mnt/sdb/qemu/block/backup-top.c:190
  #5 0x564c0d7001be (./x86_64-softmmu/qemu-system-x86_64+0x3df41be)  
/mnt/sdb/qemu/block/backup.c:439
  #6 0x564c0c8ebef8 (./x86_64-softmmu/qemu-system-x86_64+0x2fdfef8)  
/mnt/sdb/qemu/blockdev.c:3580
  #7 0x564c0c8ed0cb (./x86_64-softmmu/qemu-system-x86_64+0x2fe10cb)  
/mnt/sdb/qemu/blockdev.c:3690
  #8 0x564c0c8ed177 (./x86_64-softmmu/qemu-system-x86_64+0x2fe1177)  
/mnt/sdb/qemu/blockdev.c:3704
  #9 0x564c0d316388 (./x86_64-softmmu/qemu-system-x86_64+0x3a0a388)  
/mnt/sdb/qemu/build/qapi/qapi-commands-block-core.c:439
  #10 0x564c0d7ff7fa (./x86_64-softmmu/qemu-system-x86_64+0x3ef37fa)  
/mnt/sdb/qemu/qapi/qmp-dispatch.c:132
  #11 0x564c0d7ffcb8 (./x86_64-softmmu/qemu-system-x86_64+0x3ef3cb8)  
/mnt/sdb/qemu/qapi/qmp-dispatch.c:175 (discriminator 4)
  #12 0x564c0d2704ef (./x86_64-softmmu/qemu-system-x86_64+0x39644ef)  
/mnt/sdb/qemu/monitor/qmp.c:145
  #13 0x564c0d2712de (./x86_64-softmmu/qemu-system-x86_64+0x39652de)  
/mnt/sdb/qemu/monitor/qmp.c:234 (discriminator 4)

Reported-by: Euler Robot <address@hidden>
Signed-off-by: Pan Nengyuan <address@hidden>
---
 block/backup-top.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/backup-top.c b/block/backup-top.c
index 818d3f26b4..d565f05520 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -196,6 +196,7 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState 
*source,
     }
 
     top->total_sectors = source->total_sectors;
+    g_free(top->opaque);
     top->opaque = state = g_new0(BDRVBackupTopState, 1);
 
     bdrv_ref(target);
-- 
2.21.0.windows.1