umd: Rename umd_info.cmdline umd_info.driver_name

The only thing supplied in the cmdline today is the driver name so
rename the field to clarify the code.

As this value is always supplied stop trying to handle the case of
a NULL cmdline.

Additionally since we now have a name we can count on use the
driver_name any place where the code is looking for a name
of the binary.

v1: https://lkml.kernel.org/r/87imfef0k3.fsf_-_@x220.int.ebiederm.org
v2: https://lkml.kernel.org/r/87366d63os.fsf_-_@x220.int.ebiederm.org
Link: https://lkml.kernel.org/r/20200702164140.4468-7-ebiederm@xmission.com
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

include/linux/usermode_driver.h

@@ -18,7 +18,7 @@ static inline void exit_umh(struct task_struct *tsk)
 #endif
 
 struct umd_info {
-	const char *cmdline;
+	const char *driver_name;
 	struct file *pipe_to_umh;
 	struct file *pipe_from_umh;
 	struct list_head list;

kernel/usermode_driver.c

@@ -67,9 +67,6 @@ static void umd_cleanup(struct subprocess_info *info)
  * @len: length of the blob
  * @info: information about usermode process (shouldn't be NULL)
  *
- * If info->cmdline is set it will be used as command line for the
- * user process, else "usermodehelper" is used.
- *
  * Returns either negative error or zero which indicates success
  * in executing a blob of bytes as a usermode process. In such
  * case 'struct umd_info *info' is populated with two pipes
@@ -79,7 +76,6 @@ static void umd_cleanup(struct subprocess_info *info)
  */
 int fork_usermode_blob(void *data, size_t len, struct umd_info *info)
 {
-	const char *cmdline = (info->cmdline) ? info->cmdline : "usermodehelper";
 	struct subprocess_info *sub_info;
 	char **argv = NULL;
 	struct file *file;
@@ -87,7 +83,7 @@ int fork_usermode_blob(void *data, size_t len, struct umd_info *info)
 	loff_t pos = 0;
 	int err;
 
-	file = shmem_kernel_file_setup("", len, 0);
+	file = shmem_kernel_file_setup(info->driver_name, len, 0);
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
@@ -100,11 +96,12 @@ int fork_usermode_blob(void *data, size_t len, struct umd_info *info)
 	}
 
 	err = -ENOMEM;
-	argv = argv_split(GFP_KERNEL, cmdline, NULL);
+	argv = argv_split(GFP_KERNEL, info->driver_name, NULL);
 	if (!argv)
 		goto out;
 
-	sub_info = call_usermodehelper_setup("none", argv, NULL, GFP_KERNEL,
+	sub_info = call_usermodehelper_setup(info->driver_name, argv, NULL,
+					     GFP_KERNEL,
 					     umd_setup, umd_cleanup, info);
 	if (!sub_info)
 		goto out;

net/ipv4/bpfilter/sockopt.c

@@ -70,7 +70,7 @@ static int __init bpfilter_sockopt_init(void)
 {
 	mutex_init(&bpfilter_ops.lock);
 	bpfilter_ops.stop = true;
-	bpfilter_ops.info.cmdline = "bpfilter_umh";
+	bpfilter_ops.info.driver_name = "bpfilter_umh";
 	bpfilter_ops.info.cleanup = &bpfilter_umh_cleanup;
 
 	return 0;