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![Oleg Nesterov](/assets/img/avatar_default.png)
allow_signal(SIGCHLD) does all necessary job, no need to call do_sigaction() prior to. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
350 lines
9.5 KiB
C
350 lines
9.5 KiB
C
/*
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kmod, the new module loader (replaces kerneld)
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Kirk Petersen
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Reorganized not to be a daemon by Adam Richter, with guidance
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from Greg Zornetzer.
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Modified to avoid chroot and file sharing problems.
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Mikael Pettersson
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Limit the concurrent number of kmod modprobes to catch loops from
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"modprobe needs a service that is in a module".
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Keith Owens <kaos@ocs.com.au> December 1999
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Unblock all signals when we exec a usermode process.
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Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
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call_usermodehelper wait flag, and remove exec_usermodehelper.
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Rusty Russell <rusty@rustcorp.com.au> Jan 2003
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*/
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/syscalls.h>
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#include <linux/unistd.h>
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#include <linux/kmod.h>
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#include <linux/slab.h>
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#include <linux/mnt_namespace.h>
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#include <linux/completion.h>
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#include <linux/file.h>
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#include <linux/workqueue.h>
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#include <linux/security.h>
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#include <linux/mount.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/resource.h>
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#include <asm/uaccess.h>
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extern int max_threads;
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static struct workqueue_struct *khelper_wq;
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#ifdef CONFIG_KMOD
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/*
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modprobe_path is set via /proc/sys.
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*/
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char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
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/**
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* request_module - try to load a kernel module
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* @fmt: printf style format string for the name of the module
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* @varargs: arguements as specified in the format string
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*
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* Load a module using the user mode module loader. The function returns
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* zero on success or a negative errno code on failure. Note that a
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* successful module load does not mean the module did not then unload
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* and exit on an error of its own. Callers must check that the service
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* they requested is now available not blindly invoke it.
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*
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* If module auto-loading support is disabled then this function
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* becomes a no-operation.
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*/
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int request_module(const char *fmt, ...)
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{
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va_list args;
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char module_name[MODULE_NAME_LEN];
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unsigned int max_modprobes;
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int ret;
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char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
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static char *envp[] = { "HOME=/",
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"TERM=linux",
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"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
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NULL };
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static atomic_t kmod_concurrent = ATOMIC_INIT(0);
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#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
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static int kmod_loop_msg;
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va_start(args, fmt);
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ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
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va_end(args);
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if (ret >= MODULE_NAME_LEN)
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return -ENAMETOOLONG;
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/* If modprobe needs a service that is in a module, we get a recursive
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* loop. Limit the number of running kmod threads to max_threads/2 or
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* MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
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* would be to run the parents of this process, counting how many times
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* kmod was invoked. That would mean accessing the internals of the
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* process tables to get the command line, proc_pid_cmdline is static
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* and it is not worth changing the proc code just to handle this case.
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* KAO.
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*
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* "trace the ppid" is simple, but will fail if someone's
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* parent exits. I think this is as good as it gets. --RR
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*/
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max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
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atomic_inc(&kmod_concurrent);
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if (atomic_read(&kmod_concurrent) > max_modprobes) {
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/* We may be blaming an innocent here, but unlikely */
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if (kmod_loop_msg++ < 5)
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printk(KERN_ERR
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"request_module: runaway loop modprobe %s\n",
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module_name);
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atomic_dec(&kmod_concurrent);
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return -ENOMEM;
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}
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ret = call_usermodehelper(modprobe_path, argv, envp, 1);
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atomic_dec(&kmod_concurrent);
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return ret;
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}
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EXPORT_SYMBOL(request_module);
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#endif /* CONFIG_KMOD */
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struct subprocess_info {
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struct work_struct work;
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struct completion *complete;
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char *path;
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char **argv;
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char **envp;
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struct key *ring;
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int wait;
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int retval;
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struct file *stdin;
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};
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/*
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* This is the task which runs the usermode application
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*/
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static int ____call_usermodehelper(void *data)
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{
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struct subprocess_info *sub_info = data;
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struct key *new_session, *old_session;
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int retval;
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/* Unblock all signals and set the session keyring. */
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new_session = key_get(sub_info->ring);
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spin_lock_irq(¤t->sighand->siglock);
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old_session = __install_session_keyring(current, new_session);
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flush_signal_handlers(current, 1);
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sigemptyset(¤t->blocked);
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recalc_sigpending();
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spin_unlock_irq(¤t->sighand->siglock);
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key_put(old_session);
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/* Install input pipe when needed */
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if (sub_info->stdin) {
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struct files_struct *f = current->files;
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struct fdtable *fdt;
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/* no races because files should be private here */
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sys_close(0);
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fd_install(0, sub_info->stdin);
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spin_lock(&f->file_lock);
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fdt = files_fdtable(f);
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FD_SET(0, fdt->open_fds);
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FD_CLR(0, fdt->close_on_exec);
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spin_unlock(&f->file_lock);
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/* and disallow core files too */
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current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
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}
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/* We can run anywhere, unlike our parent keventd(). */
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set_cpus_allowed(current, CPU_MASK_ALL);
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/*
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* Our parent is keventd, which runs with elevated scheduling priority.
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* Avoid propagating that into the userspace child.
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*/
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set_user_nice(current, 0);
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retval = -EPERM;
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if (current->fs->root)
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retval = kernel_execve(sub_info->path,
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sub_info->argv, sub_info->envp);
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/* Exec failed? */
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sub_info->retval = retval;
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do_exit(0);
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}
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/* Keventd can't block, but this (a child) can. */
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static int wait_for_helper(void *data)
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{
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struct subprocess_info *sub_info = data;
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pid_t pid;
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/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
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* populate the status, but will return -ECHILD. */
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allow_signal(SIGCHLD);
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pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
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if (pid < 0) {
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sub_info->retval = pid;
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} else {
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int ret;
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/*
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* Normally it is bogus to call wait4() from in-kernel because
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* wait4() wants to write the exit code to a userspace address.
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* But wait_for_helper() always runs as keventd, and put_user()
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* to a kernel address works OK for kernel threads, due to their
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* having an mm_segment_t which spans the entire address space.
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*
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* Thus the __user pointer cast is valid here.
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*/
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sys_wait4(pid, (int __user *)&ret, 0, NULL);
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/*
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* If ret is 0, either ____call_usermodehelper failed and the
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* real error code is already in sub_info->retval or
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* sub_info->retval is 0 anyway, so don't mess with it then.
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*/
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if (ret)
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sub_info->retval = ret;
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}
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if (sub_info->wait < 0)
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kfree(sub_info);
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else
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complete(sub_info->complete);
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return 0;
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}
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/* This is run by khelper thread */
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static void __call_usermodehelper(struct work_struct *work)
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{
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struct subprocess_info *sub_info =
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container_of(work, struct subprocess_info, work);
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pid_t pid;
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int wait = sub_info->wait;
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/* CLONE_VFORK: wait until the usermode helper has execve'd
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* successfully We need the data structures to stay around
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* until that is done. */
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if (wait)
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pid = kernel_thread(wait_for_helper, sub_info,
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CLONE_FS | CLONE_FILES | SIGCHLD);
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else
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pid = kernel_thread(____call_usermodehelper, sub_info,
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CLONE_VFORK | SIGCHLD);
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if (wait < 0)
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return;
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if (pid < 0) {
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sub_info->retval = pid;
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complete(sub_info->complete);
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} else if (!wait)
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complete(sub_info->complete);
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}
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/**
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* call_usermodehelper_keys - start a usermode application
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* @path: pathname for the application
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* @argv: null-terminated argument list
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* @envp: null-terminated environment list
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* @session_keyring: session keyring for process (NULL for an empty keyring)
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* @wait: wait for the application to finish and return status.
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* when -1 don't wait at all, but you get no useful error back when
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* the program couldn't be exec'ed. This makes it safe to call
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* from interrupt context.
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*
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* Runs a user-space application. The application is started
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* asynchronously if wait is not set, and runs as a child of keventd.
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* (ie. it runs with full root capabilities).
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*
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* Must be called from process context. Returns a negative error code
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* if program was not execed successfully, or 0.
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*/
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int call_usermodehelper_keys(char *path, char **argv, char **envp,
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struct key *session_keyring, int wait)
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{
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DECLARE_COMPLETION_ONSTACK(done);
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struct subprocess_info *sub_info;
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int retval;
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if (!khelper_wq)
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return -EBUSY;
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if (path[0] == '\0')
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return 0;
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sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
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if (!sub_info)
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return -ENOMEM;
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INIT_WORK(&sub_info->work, __call_usermodehelper);
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sub_info->complete = &done;
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sub_info->path = path;
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sub_info->argv = argv;
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sub_info->envp = envp;
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sub_info->ring = session_keyring;
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sub_info->wait = wait;
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queue_work(khelper_wq, &sub_info->work);
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if (wait < 0) /* task has freed sub_info */
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return 0;
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wait_for_completion(&done);
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retval = sub_info->retval;
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kfree(sub_info);
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return retval;
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}
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EXPORT_SYMBOL(call_usermodehelper_keys);
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int call_usermodehelper_pipe(char *path, char **argv, char **envp,
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struct file **filp)
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{
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DECLARE_COMPLETION(done);
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struct subprocess_info sub_info = {
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.work = __WORK_INITIALIZER(sub_info.work,
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__call_usermodehelper),
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.complete = &done,
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.path = path,
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.argv = argv,
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.envp = envp,
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.retval = 0,
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};
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struct file *f;
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if (!khelper_wq)
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return -EBUSY;
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if (path[0] == '\0')
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return 0;
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f = create_write_pipe();
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if (IS_ERR(f))
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return PTR_ERR(f);
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*filp = f;
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f = create_read_pipe(f);
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if (IS_ERR(f)) {
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free_write_pipe(*filp);
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return PTR_ERR(f);
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}
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sub_info.stdin = f;
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queue_work(khelper_wq, &sub_info.work);
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wait_for_completion(&done);
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return sub_info.retval;
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}
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EXPORT_SYMBOL(call_usermodehelper_pipe);
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void __init usermodehelper_init(void)
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{
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khelper_wq = create_singlethread_workqueue("khelper");
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BUG_ON(!khelper_wq);
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}
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