cxl/mbox: Use type __u32 for mailbox payload sizes

Payload sizes for mailbox commands are expected to be positive values
coming from userspace. The documentation correctly describes these as
always unsigned values. The mailbox and send structures that support
the mailbox commands however, use __s32 types for the payloads.

Replace  __s32 with __u32 in the mailbox and send command structures
and update usages.

Kernel users of the interface already block all negative values and
there is no known ability for userspace to have grown a dependency on
submitting negative values to the kernel. The known user of the IOCTL,
the CXL command line interface (cxl-cli) already enforces positive
size values.

A Smatch warning of a signedness uncovered this issue.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/r/20220414051246.1244575-1-alison.schofield@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 8a8388599a85..d54a6d175fff 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -35,6 +35,7 @@ static bool cxl_raw_allow_all;
 	.flags = _flags,                                                       \
 	}
 
+#define CXL_VARIABLE_PAYLOAD	~0U
 /*
  * This table defines the supported mailbox commands for the driver. This table
  * is made up of a UAPI structure. Non-negative values as parameters in the
@@ -44,26 +45,26 @@ static bool cxl_raw_allow_all;
 static struct cxl_mem_command cxl_mem_commands[CXL_MEM_COMMAND_ID_MAX] = {
 	CXL_CMD(IDENTIFY, 0, 0x43, CXL_CMD_FLAG_FORCE_ENABLE),
 #ifdef CONFIG_CXL_MEM_RAW_COMMANDS
-	CXL_CMD(RAW, ~0, ~0, 0),
+	CXL_CMD(RAW, CXL_VARIABLE_PAYLOAD, CXL_VARIABLE_PAYLOAD, 0),
 #endif
-	CXL_CMD(GET_SUPPORTED_LOGS, 0, ~0, CXL_CMD_FLAG_FORCE_ENABLE),
+	CXL_CMD(GET_SUPPORTED_LOGS, 0, CXL_VARIABLE_PAYLOAD, CXL_CMD_FLAG_FORCE_ENABLE),
 	CXL_CMD(GET_FW_INFO, 0, 0x50, 0),
 	CXL_CMD(GET_PARTITION_INFO, 0, 0x20, 0),
-	CXL_CMD(GET_LSA, 0x8, ~0, 0),
+	CXL_CMD(GET_LSA, 0x8, CXL_VARIABLE_PAYLOAD, 0),
 	CXL_CMD(GET_HEALTH_INFO, 0, 0x12, 0),
-	CXL_CMD(GET_LOG, 0x18, ~0, CXL_CMD_FLAG_FORCE_ENABLE),
+	CXL_CMD(GET_LOG, 0x18, CXL_VARIABLE_PAYLOAD, CXL_CMD_FLAG_FORCE_ENABLE),
 	CXL_CMD(SET_PARTITION_INFO, 0x0a, 0, 0),
-	CXL_CMD(SET_LSA, ~0, 0, 0),
+	CXL_CMD(SET_LSA, CXL_VARIABLE_PAYLOAD, 0, 0),
 	CXL_CMD(GET_ALERT_CONFIG, 0, 0x10, 0),
 	CXL_CMD(SET_ALERT_CONFIG, 0xc, 0, 0),
 	CXL_CMD(GET_SHUTDOWN_STATE, 0, 0x1, 0),
 	CXL_CMD(SET_SHUTDOWN_STATE, 0x1, 0, 0),
-	CXL_CMD(GET_POISON, 0x10, ~0, 0),
+	CXL_CMD(GET_POISON, 0x10, CXL_VARIABLE_PAYLOAD, 0),
 	CXL_CMD(INJECT_POISON, 0x8, 0, 0),
 	CXL_CMD(CLEAR_POISON, 0x48, 0, 0),
 	CXL_CMD(GET_SCAN_MEDIA_CAPS, 0x10, 0x4, 0),
 	CXL_CMD(SCAN_MEDIA, 0x11, 0, 0),
-	CXL_CMD(GET_SCAN_MEDIA, 0, ~0, 0),
+	CXL_CMD(GET_SCAN_MEDIA, 0, CXL_VARIABLE_PAYLOAD, 0),
 };
 
 /*
@@ -187,9 +188,10 @@ int cxl_mbox_send_cmd(struct cxl_dev_state *cxlds, u16 opcode, void *in,
 	 * Variable sized commands can't be validated and so it's up to the
 	 * caller to do that if they wish.
 	 */
-	if (cmd->info.size_out >= 0 && mbox_cmd.size_out != out_size)
-		return -EIO;
-
+	if (cmd->info.size_out != CXL_VARIABLE_PAYLOAD) {
+		if (mbox_cmd.size_out != out_size)
+			return -EIO;
+	}
 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_mbox_send_cmd, CXL);
@@ -275,7 +277,7 @@ static int cxl_mbox_cmd_ctor(struct cxl_mbox_cmd *mbox,
 	}
 
 	/* Prepare to handle a full payload for variable sized output */
-	if (out_size < 0)
+	if (out_size == CXL_VARIABLE_PAYLOAD)
 		mbox->size_out = cxlds->payload_size;
 	else
 		mbox->size_out = out_size;
@@ -353,11 +355,11 @@ static int cxl_to_mem_cmd(struct cxl_mem_command *mem_cmd,
 		return -EBUSY;
 
 	/* Check the input buffer is the expected size */
-	if (info->size_in >= 0 && info->size_in != send_cmd->in.size)
+	if (info->size_in != send_cmd->in.size)
 		return -ENOMEM;
 
 	/* Check the output buffer is at least large enough */
-	if (info->size_out >= 0 && send_cmd->out.size < info->size_out)
+	if (send_cmd->out.size < info->size_out)
 		return -ENOMEM;
 
 	*mem_cmd = (struct cxl_mem_command) {