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SubjectRe: [PATCH V2] nvme-rdma: fix double free in nvme_rdma_free_queue
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Hi Jianchao,

On 5/10/2018 12:42 PM, Jianchao Wang wrote:
> BUG: KASAN: double-free or invalid-free in nvme_rdma_free_queue+0xf6/0x110 [nvme_rdma]
> Workqueue: nvme-reset-wq nvme_rdma_reset_ctrl_work [nvme_rdma]
> Call Trace:
> dump_stack+0x91/0xeb
> print_address_description+0x6b/0x290
> kasan_report_invalid_free+0x55/0x80
> __kasan_slab_free+0x176/0x190
> kfree+0xeb/0x310
> nvme_rdma_free_queue+0xf6/0x110 [nvme_rdma]
> nvme_rdma_configure_admin_queue+0x1a3/0x4d0 [nvme_rdma]
> nvme_rdma_reset_ctrl_work+0x4e/0xd0 [nvme_rdma]
> process_one_work+0x3ca/0xaa0
> worker_thread+0x4e2/0x6c0
> kthread+0x18d/0x1e0
> ret_from_fork+0x24/0x30
>
> The double free is on ctrl->async_event_sqe.
> If any case fails before ctrl->async_event_sqe is allocated in
> nvme_rdma_configure_admin_queue, nvme_rdma_free_queue will be
> invoked. However, at the moment, the ctrl->async_event_sqe has
> not been allocated because it has been freed in
> nvme_rdma_reset_ctrl_work
> -> nvme_rdma_shutdown_ctrl
> ->nvme_rdma_destroy_admin_queue
> -> nvme_rdma_free_queue
>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
> ---
>
> V2:
> handle it in nvme_rdma_free_queue and add some comment to explain it.

I don't know exactly what Christoph meant but IMO the best place to
allocate it is in nvme_rdma_alloc_queue just before calling

"set_bit(NVME_RDMA_Q_ALLOCATED, &queue->flags);"

then you will never get to double free since we clear the
NVME_RDMA_Q_ALLOCATED bit in the beginning of nvme_rdma_free_queue.

>
> drivers/nvme/host/rdma.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
> index 966e0dd..fa5cf87 100644
> --- a/drivers/nvme/host/rdma.c
> +++ b/drivers/nvme/host/rdma.c
> @@ -561,9 +561,18 @@ static void nvme_rdma_free_queue(struct nvme_rdma_queue *queue)
> return;
>
> if (nvme_rdma_queue_idx(queue) == 0) {
> - nvme_rdma_free_qe(queue->device->dev,
> - &queue->ctrl->async_event_sqe,
> - sizeof(struct nvme_command), DMA_TO_DEVICE);
> + /*
> + * async_event_sqe is not allocated in nvme_rdma_alloc_queue.
> + * so there are cases where NVME_RDMA_Q_ALLOCATED is set, but
> + * async_event_sqe is not allocated. To avoid double free, set
> + * async_event_sqe.data to NULL to indicate it has been freed.
> + */
> + if (queue->ctrl->async_event_sqe.data) {
> + nvme_rdma_free_qe(queue->device->dev,
> + &queue->ctrl->async_event_sqe,
> + sizeof(struct nvme_command), DMA_TO_DEVICE);
> + queue->ctrl->async_event_sqe.data = NULL;
> + }
> }
>
> nvme_rdma_destroy_queue_ib(queue);
>


-Max.

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