Re: [PATCH V2] block/nbd: fix memory leak in nbd_open()

[Stefano Garzarella]

On Thu, Nov 28, 2019 at 08:09:31PM +0800, address@hidden wrote:
> 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>
> ---
> Changes v2 to v1:
> - add a new function to do the common cleanups (suggested by Stefano 
> Garzarella).
> ---
>  block/nbd.c | 26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/block/nbd.c b/block/nbd.c
> index 1239761..f8aa2a8 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -94,6 +94,8 @@ typedef struct BDRVNBDState {
>  
>  static int nbd_client_connect(BlockDriverState *bs, Error **errp);
>  
> +static void nbd_free_bdrvstate_prop(BDRVNBDState *s);
> +
>  static void nbd_channel_error(BDRVNBDState *s, int ret)
>  {
>      if (ret == -EIO) {
> @@ -1486,6 +1488,17 @@ static int nbd_client_connect(BlockDriverState *bs, 
> Error **errp)
>      }
>  }
>  
> +static void nbd_free_bdrvstate_prop(BDRVNBDState *s)
> +{
> +    object_unref(OBJECT(s->tlscreds));
> +    qapi_free_SocketAddress(s->saddr);
> +    g_free(s->export);
> +    g_free(s->tlscredsid);
> +    if (s->x_dirty_bitmap) {
       ^ it is not needed, g_free() handles NULL pointers.
> +        g_free(s->x_dirty_bitmap);
> +    }
> +}
> +

Please, split this patch in two patches:
- the first patch where you add this function and use it in
  nbd_process_options() and nbd_close()
- the second patch where you fix the leak in nbd_open()

Thanks,
Stefano

>  /*
>   * Parse nbd_open options
>   */
> @@ -1855,10 +1868,7 @@ static int nbd_process_options(BlockDriverState *bs, 
> QDict *options,
>  
>   error:
>      if (ret < 0) {
> -        object_unref(OBJECT(s->tlscreds));
> -        qapi_free_SocketAddress(s->saddr);
> -        g_free(s->export);
> -        g_free(s->tlscredsid);
> +        nbd_free_bdrvstate_prop(s);
>      }
>      qemu_opts_del(opts);
>      return ret;
> @@ -1881,6 +1891,7 @@ static int nbd_open(BlockDriverState *bs, QDict 
> *options, int flags,
>  
>      ret = nbd_client_connect(bs, errp);
>      if (ret < 0) {
> +        nbd_free_bdrvstate_prop(s);
>          return ret;
>      }
>      /* successfully connected */
> @@ -1937,12 +1948,7 @@ static void nbd_close(BlockDriverState *bs)
>      BDRVNBDState *s = bs->opaque;
>  
>      nbd_client_close(bs);
> -
> -    object_unref(OBJECT(s->tlscreds));
> -    qapi_free_SocketAddress(s->saddr);
> -    g_free(s->export);
> -    g_free(s->tlscredsid);
> -    g_free(s->x_dirty_bitmap);
> +    nbd_free_bdrvstate_prop(s);
>  }
>  
>  static int64_t nbd_getlength(BlockDriverState *bs)
> -- 
> 2.7.2.windows.1
> 
> 
> 

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