[PATCH V2 1/2] nvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers

[Hannes Reinecke]

On 3/13/26 08:45, Maurizio Lombardi wrote:
> On Fri Mar 13, 2026 at 8:10 AM CET, Hannes Reinecke wrote:
>> On 3/12/26 14:40, Maurizio Lombardi wrote:
>>> Currently, when nvmet_tcp_build_pdu_iovec() detects an out-of-bounds
>>> PDU length or offset, it triggers nvmet_tcp_fatal_error(cmd->queue)
>>> and returns early. However, because the function returns void, the
>>> callers are entirely unaware that a fatal error has occurred and
>>> that the cmd->recv_msg.msg_iter was left uninitialized.
>>>
>>> Callers such as nvmet_tcp_handle_h2c_data_pdu() proceed to blindly
>>> overwrite the queue state with queue->rcv_state = NVMET_TCP_RECV_DATA
>>> Consequently, the socket receiving loop may attempt to read incoming
>>> network data into the uninitialized iterator.
>>>
>>> Fix this by shifting the error handling responsibility to the callers.
>>>
>>> Fixes: 52a0a9854934 ("nvmet-tcp: add bounds checks in nvmet_tcp_build_pdu_iovec")
>>> Signed-off-by: Maurizio Lombardi <mlombard at redhat.com>
>>> ---
>>>    drivers/nvme/target/tcp.c | 51 ++++++++++++++++++++++-----------------
>>>    1 file changed, 29 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
>>> index acc71a26733f..1fbf12df1183 100644
>>> --- a/drivers/nvme/target/tcp.c
>>> +++ b/drivers/nvme/target/tcp.c
>>> @@ -351,7 +351,7 @@ static void nvmet_tcp_free_cmd_buffers(struct nvmet_tcp_cmd *cmd)
>>>    
>>>    static void nvmet_tcp_fatal_error(struct nvmet_tcp_queue *queue);
>>>    
>>> -static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
>>> +static int nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
>>>    {
>>>    	struct bio_vec *iov = cmd->iov;
>>>    	struct scatterlist *sg;
>>> @@ -364,22 +364,19 @@ static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
>>>    	offset = cmd->rbytes_done;
>>>    	cmd->sg_idx = offset / PAGE_SIZE;
>>>    	sg_offset = offset % PAGE_SIZE;
>>> -	if (!cmd->req.sg_cnt || cmd->sg_idx >= cmd->req.sg_cnt) {
>>> -		nvmet_tcp_fatal_error(cmd->queue);
>>> -		return;
>>> -	}
>>> +	if (!cmd->req.sg_cnt || cmd->sg_idx >= cmd->req.sg_cnt)
>>> +		return -EPROTO;
>>> +
>>>    	sg = &cmd->req.sg[cmd->sg_idx];
>>>    	sg_remaining = cmd->req.sg_cnt - cmd->sg_idx;
>>>    
>>>    	while (length) {
>>> -		if (!sg_remaining) {
>>> -			nvmet_tcp_fatal_error(cmd->queue);
>>> -			return;
>>> -		}
>>> -		if (!sg->length || sg->length <= sg_offset) {
>>> -			nvmet_tcp_fatal_error(cmd->queue);
>>> -			return;
>>> -		}
>>> +		if (!sg_remaining)
>>> +			return -EPROTO;
>>> +
>>> +		if (!sg->length || sg->length <= sg_offset)
>>> +			return -EPROTO;
>>> +
>>>    		u32 iov_len = min_t(u32, length, sg->length - sg_offset);
>>>    
>>>    		bvec_set_page(iov, sg_page(sg), iov_len,
>>> @@ -394,6 +391,7 @@ static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
>>>    
>>>    	iov_iter_bvec(&cmd->recv_msg.msg_iter, ITER_DEST, cmd->iov,
>>>    		      nr_pages, cmd->pdu_len);
>>> +	return 0;
>>>    }
>>>    
>>>    static void nvmet_tcp_fatal_error(struct nvmet_tcp_queue *queue)
>>> @@ -931,7 +929,7 @@ static int nvmet_tcp_handle_icreq(struct nvmet_tcp_queue *queue)
>>>    	return 0;
>>>    }
>>>    
>>> -static void nvmet_tcp_handle_req_failure(struct nvmet_tcp_queue *queue,
>>> +static int nvmet_tcp_handle_req_failure(struct nvmet_tcp_queue *queue,
>>>    		struct nvmet_tcp_cmd *cmd, struct nvmet_req *req)
>>>    {
>>>    	size_t data_len = le32_to_cpu(req->cmd->common.dptr.sgl.length);
>>> @@ -947,19 +945,23 @@ static void nvmet_tcp_handle_req_failure(struct nvmet_tcp_queue *queue,
>>>    	if (!nvme_is_write(cmd->req.cmd) || !data_len ||
>>>    	    data_len > cmd->req.port->inline_data_size) {
>>>    		nvmet_prepare_receive_pdu(queue);
>>> -		return;
>>> +		return 0;
>>>    	}
>>>    
>>>    	ret = nvmet_tcp_map_data(cmd);
>>>    	if (unlikely(ret)) {
>>>    		pr_err("queue %d: failed to map data\n", queue->idx);
>>>    		nvmet_tcp_fatal_error(queue);
>>> -		return;
>>> +		return -EPROTO;
>>>    	}
>>>    
>>>    	queue->rcv_state = NVMET_TCP_RECV_DATA;
>>> -	nvmet_tcp_build_pdu_iovec(cmd);
>>>    	cmd->flags |= NVMET_TCP_F_INIT_FAILED;
>>> +	ret = nvmet_tcp_build_pdu_iovec(cmd);
>>> +	if (unlikely(ret))
>>> +		pr_err("queue %d: failed to build PDU iovec\n", queue->idx);
>>
>> Why don't we call 'nvmet_tcp_fatal_error()' here?
>> The original code did ...
> 
> We don't need too, the error code is propagated up to
> nvmet_tcp_done_recv_pdu, then up to nvmet_tcp_try_recv_pdu()
> and then up to nvmet_tcp_try_recv_one(). Finally, it reaches
> nvmet_tcp_try_recv() that checks the error code and calls
> nvmet_tcp_socket_error(), because the error code is -EPROTO
> nvmet_tcp_fatal_error() will be called.
> 
Ah, got it.

Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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