Re: [PATCH] nvme: prevent double free in nvme_alloc_ns() error handling

[Javier GonzÃlez]

On 27.04.2020 14:34, Niklas Cassel wrote:
> When jumping to the out_put_disk label, we will call put_disk(), which will
> trigger a call to disk_release(), which calls blk_put_queue().
>
> Later in the cleanup code, we do blk_cleanup_queue(), which will also call
> blk_put_queue().
>
> Putting the queue twice is incorrect, and will generate a KASAN splat.
>
> Set the disk->queue pointer to NULL, before calling put_disk(), so that the
> first call to blk_put_queue() will not free the queue.
>
> The second call to blk_put_queue() uses another pointer to the same queue,
> so this call will still free the queue.
>
> Fixes: 85136c010285 ("lightnvm: simplify geometry enumeration")
> Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
> ---
> drivers/nvme/host/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 91c1bd659947..f2adea96b04c 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3642,6 +3642,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
>
> 	return;
>  out_put_disk:
> +	/* prevent double queue cleanup */
> +	ns->disk->queue = NULL;
> 	put_disk(ns->disk);
>  out_unlink_ns:
> 	mutex_lock(&ctrl->subsys->lock);
> --
> 2.25.3
What about delaying the assignment of ns->disk?

diff --git i/drivers/nvme/host/core.c w/drivers/nvme/host/core.c
index a4d8c90ee7cc..6da4a9ced945 100644
--- i/drivers/nvme/host/core.c
+++ w/drivers/nvme/host/core.c
@@ -3541,7 +3541,6 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
        disk->queue = ns->queue;
        disk->flags = flags;
        memcpy(disk->disk_name, disk_name, DISK_NAME_LEN);
-       ns->disk = disk;

        __nvme_revalidate_disk(disk, id);

@@ -3553,6 +3552,8 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
                }
        }

+       ns->disk = disk;
+
        down_write(&ctrl->namespaces_rwsem);
        list_add_tail(&ns->list, &ctrl->namespaces);
        up_write(&ctrl->namespaces_rwsem);


Javier