[OpenWrt-Devel] [PATCH procd 2/2] instance: fix pidfile attribute double free crash

[Daniel Golle]

Hi Petr,

thanks for reviewing and fixing this!

On Wed, Jan 15, 2020 at 11:30:57AM +0100, Petr Štetiar wrote:
> Commit a5af33ce9a16 ("instance: strdup string attributes") has
> introduced duplication of various string attributes in order to fix
> use-after-free, but missed handling of one `pidfile` attribute case in
> instance_config_move() where the new value of `pidfile` is being
> copied/assigned. Source of this value is then free()d in following call
> to instance_free() and then again for 2nd time during the service stop
> command handling, leading to double free crash:
> 
>  #0  unmap_chunk at src/malloc/malloc.c:515
>  #1  free at src/malloc/malloc.c:526
>  #2  instance_free (in=0xd5e300) at instance.c:1100
>  #3  instance_delete (in=0xd5e300) at instance.c:559
>  #4  instance_stop (in=0xd5e300, halt=true) at instance.c:611

Right, didn't think about that. I don't have time to get into this
right now (but will have tonight or tomorrow), but doesn't the same
also apply at least for the 'seccomp' field?


Cheers


Daniel

> 
> Ref: FS#2723
> Cc: Daniel Golle <daniel at makrotopia.org>
> Fixes: a5af33ce9a16 ("instance: strdup string attributes")
> Signed-off-by: Petr Štetiar <ynezz at true.cz>
> ---
>  service/instance.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/service/instance.c b/service/instance.c
> index ce5233807dbb..245b9629d99a 100644
> --- a/service/instance.c
> +++ b/service/instance.c
> @@ -1031,7 +1031,6 @@ instance_config_move(struct service_instance *in, struct service_instance *in_sr
>  	blobmsg_list_move(&in->jail.mount, &in_src->jail.mount);
>  	in->trigger = in_src->trigger;
>  	in->command = in_src->command;
> -	in->pidfile = in_src->pidfile;
>  	in->respawn = in_src->respawn;
>  	in->respawn_retry = in_src->respawn_retry;
>  	in->respawn_threshold = in_src->respawn_threshold;
> @@ -1042,6 +1041,10 @@ instance_config_move(struct service_instance *in, struct service_instance *in_sr
>  	in->node.avl.key = in_src->node.avl.key;
>  	in->syslog_facility = in_src->syslog_facility;
>  
> +	free(in->pidfile);
> +	if (in_src->pidfile)
> +		in->pidfile = strdup(in_src->pidfile);
> +
>  	free(in->config);
>  	in->config = in_src->config;
>  	in_src->config = NULL;

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