Re: [PATCH 6.1.y] nvme-fabrics: use reserved tag for reg read/write command

[Harshit Mogalapalli]

Hi Artem,

On 03/10/26 2:16 am, Artem Dinaburg wrote:
> From: Chunguang Xu <chunguang.xu@xxxxxxxxxx>
>
> [ Upstream commit 7dc3bfcb4c9cc58970fff6aaa48172cb224d85aa ]
>
> In some scenarios, if too many commands are issued by nvme command in
> the same time by user tasks, this may exhaust all tags of admin_q. If
> a reset (nvme reset or IO timeout) occurs before these commands finish,
> reconnect routine may fail to update nvme regs due to insufficient tags,
> which will cause kernel hang forever. In order to workaround this issue,
> maybe we can let reg_read32()/reg_read64()/reg_write32() use reserved
> tags. This maybe safe for nvmf:
>
> 1. For the disable ctrl path,  we will not issue connect command
> 2. For the enable ctrl / fw activate path, since connect and reg_xx()
>     are called serially.
>
> So the reserved tags may still be enough while reg_xx() use reserved tags.
>
> [ Backport to 6.1.y: used the older BLK_MQ_REQ_RESERVED request flag. ]

^^ Usually this line goes after upstream commit message.

> Signed-off-by: Chunguang Xu <chunguang.xu@xxxxxxxxxx>
> Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
> Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>

--> Here.


thanks,
Harshit> Assisted-by: LLM
> Signed-off-by: Artem Dinaburg <artem@xxxxxxxxxxxxxxx>
> ---
> Hi Greg, Sasha, and nvme maintainers,
>
> I am working through the small CVE backports still missing from 6.1.y.
> This one addresses CVE-2024-41082. It reserves a request tag for
> controller-register I/O during reconnect and reset.
>
> The corresponding 6.6.y backport is already in the 6.6.y stable queue.
> The fix is already present in 6.12.y, 6.18.y, and 7.2.y, but not
> in 6.1.y.
> The target-specific adjustment is recorded in the bracketed note above.
>
> Could you please queue it for 6.1.y?
>
> CVE: CVE-2024-41082
> Upstream: 7dc3bfcb4c9cc58970fff6aaa48172cb224d85aa
>
> AI assistance: An LLM helped identify, adapt, and validate this backport; I
> reviewed the resulting code and validation evidence.
>
> Thanks,
> Artem Dinaburg
>
>   drivers/nvme/host/fabrics.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
> index ffe433c4708941..2d0dace26d8f78 100644
> --- a/drivers/nvme/host/fabrics.c
> +++ b/drivers/nvme/host/fabrics.c
> @@ -153,7 +153,7 @@ int nvmf_reg_read32(struct nvme_ctrl *ctrl, u32 off, u32 *val)
>   	cmd.prop_get.offset = cpu_to_le32(off);
>   
>   	ret = __nvme_submit_sync_cmd(ctrl->fabrics_q, &cmd, &res, NULL, 0,
> -			NVME_QID_ANY, 0, 0);
> +			NVME_QID_ANY, 0, BLK_MQ_REQ_RESERVED);
>   
>   	if (ret >= 0)
>   		*val = le64_to_cpu(res.u64);
> @@ -199,7 +199,7 @@ int nvmf_reg_read64(struct nvme_ctrl *ctrl, u32 off, u64 *val)
>   	cmd.prop_get.offset = cpu_to_le32(off);
>   
>   	ret = __nvme_submit_sync_cmd(ctrl->fabrics_q, &cmd, &res, NULL, 0,
> -			NVME_QID_ANY, 0, 0);
> +			NVME_QID_ANY, 0, BLK_MQ_REQ_RESERVED);
>   
>   	if (ret >= 0)
>   		*val = le64_to_cpu(res.u64);
> @@ -244,7 +244,7 @@ int nvmf_reg_write32(struct nvme_ctrl *ctrl, u32 off, u32 val)
>   	cmd.prop_set.value = cpu_to_le64(val);
>   
>   	ret = __nvme_submit_sync_cmd(ctrl->fabrics_q, &cmd, NULL, NULL, 0,
> -			NVME_QID_ANY, 0, 0);
> +			NVME_QID_ANY, 0, BLK_MQ_REQ_RESERVED);
>   	if (unlikely(ret))
>   		dev_err(ctrl->device,
>   			"Property Set error: %d, offset %#x\n",