Re: [PATCH v2 1/1] nvmet: pci-epf: Do not complete commands twice if nvmet_req_init() fails

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

On 7/16/25 04:15, Rick Wertenbroek wrote:
> Have nvmet_req_init() and req->execute() complete failed commands.
>
> Description of the problem:
> nvmet_req_init() calls __nvmet_req_complete() internally upon failure,
> e.g., unsupported opcode, which calls the "queue_response" callback,
> this results in nvmet_pci_epf_queue_response() being called, which will
> call nvmet_pci_epf_complete_iod() if data_len is 0 or if dma_dir is
> different from DMA_TO_DEVICE. This results in a double completion as
> nvmet_pci_epf_exec_iod_work() also calls nvmet_pci_epf_complete_iod()
> when nvmet_req_init() fails.
>
> Steps to reproduce:
> On the host send a command with an unsupported opcode with nvme-cli,
> For example the admin command "security receive"
> $ sudo nvme security-recv /dev/nvme0n1 -n1 -x4096
>
> This triggers a double completion as nvmet_req_init() fails and
> nvmet_pci_epf_queue_response() is called, here iod->dma_dir is still
> in the default state of "DMA_NONE" as set by default in
> nvmet_pci_epf_alloc_iod(), so nvmet_pci_epf_complete_iod() is called.
> Because nvmet_req_init() failed nvmet_pci_epf_complete_iod() is also
> called in nvmet_pci_epf_exec_iod_work() leading to a double completion.
> This not only sends two completions to the host but also corrupts the
> state of the PCI NVMe target leading to kernel oops.
>
> This patch lets nvmet_req_init() and req->execute() complete all failed
> commands, and removes the double completion case in
> nvmet_pci_epf_exec_iod_work() therefore fixing the edge cases where
> double completions occurred.
>
> Signed-off-by: Rick Wertenbroek<rick.wertenbroek@gmail.com>
> Reviewed-by: Damien Le Moal<dlemoal@kernel.org>
> Fixes: 0faa0fe6f90e ("nvmet: New NVMe PCI endpoint function target driver")
> Cc:stable@vger.kernel.org

Good catch, looks good, I wish we have tests for this part of target
to it will get tested on regular basis, not the requirement, just
a thought.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck