nvmet: fix dsm failure when payload does not match sgl descriptor

The host is allowed to pass the controller an sgl describing a buffer
that is larger than the dsm payload itself, allow it when executing
dsm.
Reported-by: Dakshaja Uppalapati <dakshaja@chelsio.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>,
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/core.c

@@ -939,6 +939,17 @@ bool nvmet_check_data_len(struct nvmet_req *req, size_t data_len)
 }
 EXPORT_SYMBOL_GPL(nvmet_check_data_len);
 
+bool nvmet_check_data_len_lte(struct nvmet_req *req, size_t data_len)
+{
+	if (unlikely(data_len > req->transfer_len)) {
+		req->error_loc = offsetof(struct nvme_common_command, dptr);
+		nvmet_req_complete(req, NVME_SC_SGL_INVALID_DATA | NVME_SC_DNR);
+		return false;
+	}
+
+	return true;
+}
+
 int nvmet_req_alloc_sgl(struct nvmet_req *req)
 {
 	struct pci_dev *p2p_dev = NULL;

drivers/nvme/target/io-cmd-bdev.c

@@ -280,7 +280,7 @@ static void nvmet_bdev_execute_discard(struct nvmet_req *req)
 
 static void nvmet_bdev_execute_dsm(struct nvmet_req *req)
 {
-	if (!nvmet_check_data_len(req, nvmet_dsm_len(req)))
+	if (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req)))
 		return;
 
 	switch (le32_to_cpu(req->cmd->dsm.attributes)) {

drivers/nvme/target/io-cmd-file.c

@@ -336,7 +336,7 @@ static void nvmet_file_dsm_work(struct work_struct *w)
 
 static void nvmet_file_execute_dsm(struct nvmet_req *req)
 {
-	if (!nvmet_check_data_len(req, nvmet_dsm_len(req)))
+	if (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req)))
 		return;
 	INIT_WORK(&req->f.work, nvmet_file_dsm_work);
 	schedule_work(&req->f.work);

drivers/nvme/target/nvmet.h

@@ -374,6 +374,7 @@ bool nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
 		struct nvmet_sq *sq, const struct nvmet_fabrics_ops *ops);
 void nvmet_req_uninit(struct nvmet_req *req);
 bool nvmet_check_data_len(struct nvmet_req *req, size_t data_len);
+bool nvmet_check_data_len_lte(struct nvmet_req *req, size_t data_len);
 void nvmet_req_complete(struct nvmet_req *req, u16 status);
 int nvmet_req_alloc_sgl(struct nvmet_req *req);
 void nvmet_req_free_sgl(struct nvmet_req *req);