[RFC 2/2] nvme: Use CAP_FIRMWARE_UPGRADE to check user commands

[Mario Limonciello]

Software that is running with CAP_FIRMWARE_UPGRADE needs a limited
set of opcode access:
* Identify the disk
* Download firmware to the disk
* Commit the firmwware to the disk

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
---
 drivers/nvme/host/core.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f13eb4ded95f..80be3d6b7437 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1593,13 +1593,23 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 	u64 result;
 	int status;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
 	if (copy_from_user(&cmd, ucmd, sizeof(cmd)))
 		return -EFAULT;
 	if (cmd.flags)
 		return -EINVAL;
 
+	switch (cmd.opcode) {
+	case nvme_admin_identify:
+	case nvme_admin_activate_fw:
+	case nvme_admin_download_fw:
+		if (!firmware_upgrade_capable())
+			return -EACCES;
+		break;
+	default:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+	}
+
 	memset(&c, 0, sizeof(c));
 	c.common.opcode = cmd.opcode;
 	c.common.flags = cmd.flags;
@@ -1637,13 +1647,23 @@ static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 	unsigned timeout = 0;
 	int status;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
 	if (copy_from_user(&cmd, ucmd, sizeof(cmd)))
 		return -EFAULT;
 	if (cmd.flags)
 		return -EINVAL;
 
+	switch (cmd.opcode) {
+	case nvme_admin_identify:
+	case nvme_admin_activate_fw:
+	case nvme_admin_download_fw:
+		if (!firmware_upgrade_capable())
+			return -EACCES;
+		break;
+	default:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+	}
+
 	memset(&c, 0, sizeof(c));
 	c.common.opcode = cmd.opcode;
 	c.common.flags = cmd.flags;
-- 
2.25.1