[PATCHv2 2/2] nvme-pci: use sgls for all user requests if possible

[Keith Busch]

From: Keith Busch <kbusch at kernel.org>

If the device supports SGLs, use these for all user requests. This
format encodes the expected transfer length so it can catch short buffer
errors in a user command, whether it occurred accidently or maliciously.

For controllers that support SGL data mode, this is a viable mitigation
to CVE-2023-6238.

Signed-off-by: Keith Busch <kbusch at kernel.org>
---
 drivers/nvme/host/pci.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 919f173043d18..8f59ff3be8cea 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -515,7 +515,8 @@ static inline bool nvme_pci_metadata_use_sgls(struct nvme_dev *dev,
 {
 	if (!nvme_ctrl_meta_sgl_supported(&dev->ctrl))
 		return false;
-	return req->nr_integrity_segments > 1;
+	return req->nr_integrity_segments > 1 ||
+		nvme_req(req)->flags & NVME_REQ_USERCMD;
 }
 
 static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req,
@@ -533,7 +534,7 @@ static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req,
 	if (nvme_pci_metadata_use_sgls(dev, req))
 		return true;
 	if (!sgl_threshold || avg_seg_size < sgl_threshold)
-		return false;
+		return nvme_req(req)->flags & NVME_REQ_USERCMD;
 	return true;
 }
 
-- 
2.43.5