Re: [Qemu-block] [PATCH] blockjob: update nodes head while removing all bdrv

[Max Reitz]

On 10.09.19 13:07, Sergio Lopez wrote:
> block_job_remove_all_bdrv() iterates through job->nodes, calling
> bdrv_root_unref_child() for each entry. The call to the latter may
> reach child_job_[can_]set_aio_ctx(), which will also attempt to
> traverse job->nodes, potentially finding entries that where freed
> on previous iterations.
> 
> To avoid this situation, update job->nodes head on each iteration to
> ensure that already freed entries are no longer linked to the list.
> 
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1746631
> Signed-off-by: Sergio Lopez <address@hidden>
> ---
>  blockjob.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/blockjob.c b/blockjob.c
> index 6e32d1a0c0..7b1551d981 100644
> --- a/blockjob.c
> +++ b/blockjob.c
> @@ -192,6 +192,12 @@ void block_job_remove_all_bdrv(BlockJob *job)
>          BdrvChild *c = l->data;
>          bdrv_op_unblock_all(c->bs, job->blocker);
>          bdrv_root_unref_child(c);
> +        /*
> +         * The call above may reach child_job_[can_]set_aio_ctx(), which will
> +         * also traverse job->nodes, so update the head here to make sure it
> +         * doesn't attempt to process an already freed BdrvChild.
> +         */
> +        job->nodes = l->next;
>      }
>      g_slist_free(job->nodes);

But this will leak the whole list.

Max

>      job->nodes = NULL;
>

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