[Devel] Re: [PATCH 1/1] don't call pre_restore_task twice

[Matt Helsley]

On Wed, Oct 07, 2009 at 06:47:50PM -0500, Serge E. Hallyn wrote:
> Pre_restore_task is being called both before and inside
> restore_task, causing a memory leak at
> current->checkpoint_data.
> 
> Only call it once, outside restore_task.
> 
> This fixes a memory leak spotted by Dan Smith, and the
> actual bug was deduced by Matt Helsley.
> 
> Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
> Reported-by: Dan Smith <danms at us.ibm.com>
> Cc: Dan Smith <danms at us.ibm.com>
> Cc: Matt Helsley <matthltc at us.ibm.com>
> 
> Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>

Reviewed-by: Matt Helsley <matthltc at us.ibm.com>

However, I think I spotted another problem:

int pre_restore_task()
{
        sigset_t sigset;

        /* task-specific restart data: freed from post_restore_task() */
        current->checkpoint_data = kzalloc(sizeof(struct ckpt_data),
GFP_KERNEL);
        if (!current->checkpoint_data)
                return -ENOMEM;
...
}

void post_restore_task()
{
	sigprocmask(SIG_SETMASK, &current->checkpoint_data->blocked, NULL);
...
}

then in do_restore_coord():

if (ctx->uflags & RESTART_TASKSELF) {
                ret = pre_restore_task();
                ckpt_debug("pre restore task: %d\n", ret);
                if (ret < 0)
                        goto out;
...
 out:
        if (ctx->uflags & RESTART_TASKSELF)
                post_restore_task();

But if we got -ENOMEM from pre_restore_task() then I think there will be a
NULL dereference.


Cheers,
	-Matt Helsley

> ---
>  checkpoint/process.c |    4 ----
>  checkpoint/restart.c |    1 +
>  2 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/checkpoint/process.c b/checkpoint/process.c
> index 424f688..c51e036 100644
> --- a/checkpoint/process.c
> +++ b/checkpoint/process.c
> @@ -864,10 +864,6 @@ int restore_task(struct ckpt_ctx *ctx)
>  {
>  	int ret;
> 
> -	ret = pre_restore_task(ctx);
> -	if (ret < 0)
> -		goto out;
> -
>  	ret = restore_task_struct(ctx);
>  	ckpt_debug("task %d\n", ret);
>  	if (ret < 0)
> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
> index 3a58a76..fc94374 100644
> --- a/checkpoint/restart.c
> +++ b/checkpoint/restart.c
> @@ -967,6 +967,7 @@ static int do_restore_task(void)
>  	 */
>  	if (zombie) {
>  		restore_debug_exit(ctx);
> +		post_restore_task(ctx);
>  		ckpt_ctx_put(ctx);
>  		do_exit(current->exit_code);
>  	}


> -- 
> 1.5.4.3
> 
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