[PATCHv3 3/3] nvme-pci: use sgls for all user requests if possible

Keith Busch
2024-11-18T15:58:10Z

From: Keith Busch <kbusch@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. For controllers that don't support SGL, log a warning
in the passthrough path since not having the capability can corrupt
data if the interface is not use correctly.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
drivers/nvme/host/ioctl.c | 12 ++++++++++--
drivers/nvme/host/pci.c | 5 +++--
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index cb7f61e2077d0..64b5542fb3b79 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -120,12 +120,20 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
struct nvme_ns *ns = q->queuedata;
struct block_device *bdev = ns ? ns->disk->part0 : NULL;
bool supports_metadata = bdev && blk_get_integrity(bdev->bd_disk);
+ struct nvme_ctrl *ctrl = nvme_req(req)->ctrl;
bool has_metadata = meta_buffer && meta_len;
struct bio *bio = NULL;
int ret;

- if (has_metadata && !supports_metadata)
- return -EINVAL;
+ if (!nvme_ctrl_sgl_supported(ctrl))
+ dev_warn_once(ctrl->device, "using unchecked data buffer\n");
+ if (has_metadata) {
+ if (!supports_metadata)
+ return -EINVAL;
+ if (!nvme_ctrl_meta_sgl_supported(ctrl))
+ dev_warn_once(ctrl->device,
+ "using unchecked metadata buffer\n");
+ }

if (ioucmd && (ioucmd->flags & IORING_URING_CMD_FIXED)) {
struct iov_iter iter;
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index c6c3ae3a7c434..4c644bb7f0692 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