autofs: fix thinko in validate_dev_ioctl()

I was so sure the per-dentry expire timeout patch worked ok but my
testing was flawed.

In validate_dev_ioctl() the check for ioctl AUTOFS_DEV_IOCTL_TIMEOUT_CMD
should use the ioctl number not the passed in ioctl command.

Fixes: 433f9d76a010 ("autofs: add per dentry expire timeout")
Cc: <[e-mail]> # mainline only
Signed-off-by: Ian Kent <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

fs/autofs/dev-ioctl.c

···
  */
 static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
 {
+	unsigned int inr = _IOC_NR(cmd);
 	int err;
 
 	err = check_dev_ioctl_version(cmd, param);
···
 		 * check_name() return for AUTOFS_DEV_IOCTL_TIMEOUT_CMD.
 		 */
 		err = check_name(param->path);
-		if (cmd == AUTOFS_DEV_IOCTL_TIMEOUT_CMD)
+		if (inr == AUTOFS_DEV_IOCTL_TIMEOUT_CMD)
 			err = err ? 0 : -EINVAL;
 		if (err) {
 			pr_warn("invalid path supplied for cmd(0x%08x)\n",
···
 			goto out;
 		}
 	} else {
-		unsigned int inr = _IOC_NR(cmd);
-
 		if (inr == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD ||
 		    inr == AUTOFS_DEV_IOCTL_REQUESTER_CMD ||
 		    inr == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD) {