/**
* call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
* @sub_info: a subprocess_info returned by call_usermodehelper_setup
* @filp: set to the write-end of a pipe
*
* This constructs a pipe, and sets the read end to be the stdin of the
* subprocess, and returns the write-end in *@filp.
*/
int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
struct file **filp)
{
struct file *f;
f = create_write_pipe(0);
if (IS_ERR(f))
return PTR_ERR(f);
*filp = f;
f = create_read_pipe(f, 0);
if (IS_ERR(f)) {
free_write_pipe(*filp);
return PTR_ERR(f);
}
sub_info->stdin = f;
return 0;
}
/*
* This is the task which runs the usermode application
*/
static int ____call_usermodehelper(void *data)
{
struct subprocess_info *sub_info = data;
int retval;
/* Install input pipe when needed */
if (sub_info->stdin) {
struct files_struct *f = current->files;
struct fdtable *fdt;
/* no races because files should be private here */
sys_close(0);
fd_install(0, sub_info->stdin);
spin_lock(&f->file_lock);
fdt = files_fdtable(f);
FD_SET(0, fdt->open_fds);
FD_CLR(0, fdt->close_on_exec);
spin_unlock(&f->file_lock);
/* and disallow core files too */
current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
}
/* We can run anywhere, unlike our parent keventd(). */
set_cpus_allowed(current, CPU_MASK_ALL);
retval = __exec_usermodehelper(sub_info->path,
sub_info->argv, sub_info->envp, sub_info->ring);
/* Exec failed? */
sub_info->retval = retval;
do_exit(0);
}
/* Keventd can't block, but this (a child) can. */
static int wait_for_helper(void *data)
{
struct subprocess_info *sub_info = data;
pid_t pid;
struct k_sigaction sa;
/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
* populate the status, but will return -ECHILD. */
sa.sa.sa_handler = SIG_IGN;
sa.sa.sa_flags = 0;
siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
do_sigaction(SIGCHLD, &sa, NULL);
allow_signal(SIGCHLD);
pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
} else {
/*
* Normally it is bogus to call wait4() from in-kernel because
* wait4() wants to write the exit code to a userspace address.
* But wait_for_helper() always runs as keventd, and put_user()
* to a kernel address works OK for kernel threads, due to their
* having an mm_segment_t which spans the entire address space.
*
* Thus the __user pointer cast is valid here.
*/
sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
}
complete(sub_info->complete);
return 0;
}
/* This is run by khelper thread */
static void __call_usermodehelper(void *data)
{
struct subprocess_info *sub_info = data;
pid_t pid;
int wait = sub_info->wait;
/* CLONE_VFORK: wait until the usermode helper has execve'd
* successfully We need the data structures to stay around
* until that is done. */
if (wait)
pid = kernel_thread(wait_for_helper, sub_info,
CLONE_FS | CLONE_FILES | SIGCHLD);
else
pid = kernel_thread(____call_usermodehelper, sub_info,
CLONE_VFORK | SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
complete(sub_info->complete);
} else if (!wait)
complete(sub_info->complete);
}
/**
* call_usermodehelper_keys - start a usermode application
* @path: pathname for the application
* @argv: null-terminated argument list
* @envp: null-terminated environment list
* @session_keyring: session keyring for process (NULL for an empty keyring)
* @wait: wait for the application to finish and return status.
*
* Runs a user-space application. The application is started
* asynchronously if wait is not set, and runs as a child of keventd.
* (ie. it runs with full root capabilities).
*
* Must be called from process context. Returns a negative error code
* if program was not execed successfully, or 0.
*/
int call_usermodehelper_keys(char *path, char **argv, char **envp,
struct key *session_keyring, int wait)
{
DECLARE_COMPLETION_ONSTACK(done);
struct subprocess_info sub_info = {
.complete = &done,
.path = path,
.argv = argv,
.envp = envp,
.ring = session_keyring,
.wait = wait,
.retval = 0,
};
DECLARE_WORK(work, __call_usermodehelper, &sub_info);
if (!khelper_wq)
return -EBUSY;
if (path[0] == '\0')
return 0;
queue_work(khelper_wq, &work);
wait_for_completion(&done);
return sub_info.retval;
}
EXPORT_SYMBOL(call_usermodehelper_keys);
int call_usermodehelper_pipe(char *path, char **argv, char **envp,
struct file **filp)
{
DECLARE_COMPLETION(done);
struct subprocess_info sub_info = {
.complete = &done,
.path = path,
.argv = argv,
.envp = envp,
.retval = 0,
};
struct file *f;
DECLARE_WORK(work, __call_usermodehelper, &sub_info);
if (!khelper_wq)
return -EBUSY;
if (path[0] == '\0')
return 0;
f = create_write_pipe();
if (!f)
return -ENOMEM;
*filp = f;
f = create_read_pipe(f);
if (!f) {
free_write_pipe(*filp);
return -ENOMEM;
}
sub_info.stdin = f;
queue_work(khelper_wq, &work);
wait_for_completion(&done);
return sub_info.retval;
}
EXPORT_SYMBOL(call_usermodehelper_pipe);
void __init usermodehelper_init(void)
{
khelper_wq = create_singlethread_workqueue("khelper");
BUG_ON(!khelper_wq);
}
