Re: [PATCH for-5.1 2/5] qom: Plug memory leak in "info qom-tree"

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 7/14/20 6:01 PM, Markus Armbruster wrote:
> Commit e8c9e65816 "qom: Make "info qom-tree" show children sorted"
> created a memory leak, because I didn't realize
> object_get_canonical_path_component()'s value needs to be freed.
> 
> Reproducer:
> 
>     $ qemu-system-x86_64 -nodefaults -display none -S -monitor stdio
>     QEMU 5.0.50 monitor - type 'help' for more information
>     (qemu) info qom-tree
> 
> This leaks some 4500 path components, 12-13 characters on average,
> i.e. roughly 100kBytes depending on the allocator.  A couple of
> hundred "info qom-tree" here, a couple of hundred there, and soon
> enough we're talking about real memory.
> 
> Plug the leak.
> 
> Fixes: e8c9e65816f5dbfe18ad3b2be938d0d8192d459a
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  qom/qom-hmp-cmds.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/qom/qom-hmp-cmds.c b/qom/qom-hmp-cmds.c
> index 9ed8bb1c9f..aaacadacca 100644
> --- a/qom/qom-hmp-cmds.c
> +++ b/qom/qom-hmp-cmds.c
> @@ -96,8 +96,10 @@ static void print_qom_composition(Monitor *mon, Object *obj, int indent);
>  
>  static int qom_composition_compare(const void *a, const void *b, void *ignore)
>  {
> -    return g_strcmp0(a ? object_get_canonical_path_component(a) : NULL,
> -                     b ? object_get_canonical_path_component(b) : NULL);
> +    g_autofree char *ac = object_get_canonical_path_component(a);
> +    g_autofree char *bc = object_get_canonical_path_component(b);
> +
> +    return g_strcmp0(ac, bc);
>  }
>  
>  static int insert_qom_composition_child(Object *obj, void *opaque)
> 

Li Qiang set this too:
https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg04732.html