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

[Stefano Garzarella]

On Thu, Nov 28, 2019 at 04:40:10PM +0800, address@hidden wrote:

Hi,
I don't know nbd code very well, the patch LGTM, but just a comment
below:

> From: PanNengyuan <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
> 
> Reported-by: Euler Robot <address@hidden>
> Signed-off-by: PanNengyuan <address@hidden>
> ---
>  block/nbd.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/block/nbd.c b/block/nbd.c
> index 1239761..bc40a25 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -1881,6 +1881,11 @@ static int nbd_open(BlockDriverState *bs, QDict 
> *options, int flags,
>  
>      ret = nbd_client_connect(bs, errp);
>      if (ret < 0) {
> +        object_unref(OBJECT(s->tlscreds));
> +        qapi_free_SocketAddress(s->saddr);
> +        g_free(s->export);
> +        g_free(s->tlscredsid);
> +        g_free(s->x_dirty_bitmap);

Since with this patch we are doing these cleanups in 3 places (here,
nbd_close(), and nbd_process_options()), should be better to add a new
function to do these cleanups?

Maybe I'd create a series adding a patch before this one, implementing this
new function, and change this patch calling it.

Thanks,
Stefano