diff options
Diffstat (limited to 'kernel/kmod.c')
| -rw-r--r-- | kernel/kmod.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c new file mode 100644 index 0000000..eed53d4 --- /dev/null +++ b/kernel/kmod.c @@ -0,0 +1,256 @@ +/* + kmod, the new module loader (replaces kerneld) + Kirk Petersen + + Reorganized not to be a daemon by Adam Richter, with guidance + from Greg Zornetzer. + + Modified to avoid chroot and file sharing problems. + Mikael Pettersson + + Limit the concurrent number of kmod modprobes to catch loops from + "modprobe needs a service that is in a module". + Keith Owens <kaos@ocs.com.au> December 1999 + + Unblock all signals when we exec a usermode process. + Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000 + + call_usermodehelper wait flag, and remove exec_usermodehelper. + Rusty Russell <rusty@rustcorp.com.au> Jan 2003 +*/ +#define __KERNEL_SYSCALLS__ + +#include <linux/config.h> +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/syscalls.h> +#include <linux/unistd.h> +#include <linux/kmod.h> +#include <linux/smp_lock.h> +#include <linux/slab.h> +#include <linux/namespace.h> +#include <linux/completion.h> +#include <linux/file.h> +#include <linux/workqueue.h> +#include <linux/security.h> +#include <linux/mount.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <asm/uaccess.h> + +extern int max_threads; + +static struct workqueue_struct *khelper_wq; + +#ifdef CONFIG_KMOD + +/* + modprobe_path is set via /proc/sys. +*/ +char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; + +/** + * request_module - try to load a kernel module + * @fmt: printf style format string for the name of the module + * @varargs: arguements as specified in the format string + * + * Load a module using the user mode module loader. The function returns + * zero on success or a negative errno code on failure. Note that a + * successful module load does not mean the module did not then unload + * and exit on an error of its own. Callers must check that the service + * they requested is now available not blindly invoke it. + * + * If module auto-loading support is disabled then this function + * becomes a no-operation. + */ +int request_module(const char *fmt, ...) +{ + va_list args; + char module_name[MODULE_NAME_LEN]; + unsigned int max_modprobes; + int ret; + char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; + static char *envp[] = { "HOME=/", + "TERM=linux", + "PATH=/sbin:/usr/sbin:/bin:/usr/bin", + NULL }; + static atomic_t kmod_concurrent = ATOMIC_INIT(0); +#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ + static int kmod_loop_msg; + + va_start(args, fmt); + ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); + va_end(args); + if (ret >= MODULE_NAME_LEN) + return -ENAMETOOLONG; + + /* If modprobe needs a service that is in a module, we get a recursive + * loop. Limit the number of running kmod threads to max_threads/2 or + * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method + * would be to run the parents of this process, counting how many times + * kmod was invoked. That would mean accessing the internals of the + * process tables to get the command line, proc_pid_cmdline is static + * and it is not worth changing the proc code just to handle this case. + * KAO. + * + * "trace the ppid" is simple, but will fail if someone's + * parent exits. I think this is as good as it gets. --RR + */ + max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); + atomic_inc(&kmod_concurrent); + if (atomic_read(&kmod_concurrent) > max_modprobes) { + /* We may be blaming an innocent here, but unlikely */ + if (kmod_loop_msg++ < 5) + printk(KERN_ERR + "request_module: runaway loop modprobe %s\n", + module_name); + atomic_dec(&kmod_concurrent); + return -ENOMEM; + } + + ret = call_usermodehelper(modprobe_path, argv, envp, 1); + atomic_dec(&kmod_concurrent); + return ret; +} +EXPORT_SYMBOL(request_module); +#endif /* CONFIG_KMOD */ + +struct subprocess_info { + struct completion *complete; + char *path; + char **argv; + char **envp; + int wait; + int retval; +}; + +/* + * This is the task which runs the usermode application + */ +static int ____call_usermodehelper(void *data) +{ + struct subprocess_info *sub_info = data; + int retval; + + /* Unblock all signals. */ + flush_signals(current); + spin_lock_irq(¤t->sighand->siglock); + flush_signal_handlers(current, 1); + sigemptyset(¤t->blocked); + recalc_sigpending(); + spin_unlock_irq(¤t->sighand->siglock); + + /* We can run anywhere, unlike our parent keventd(). */ + set_cpus_allowed(current, CPU_MASK_ALL); + + retval = -EPERM; + if (current->fs->root) + retval = execve(sub_info->path, sub_info->argv,sub_info->envp); + + /* 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, (struct k_sigaction *)0); + 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; + + /* CLONE_VFORK: wait until the usermode helper has execve'd + * successfully We need the data structures to stay around + * until that is done. */ + if (sub_info->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 (!sub_info->wait) + complete(sub_info->complete); +} + +/** + * call_usermodehelper - start a usermode application + * @path: pathname for the application + * @argv: null-terminated argument list + * @envp: null-terminated environment list + * @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(char *path, char **argv, char **envp, int wait) +{ + DECLARE_COMPLETION(done); + struct subprocess_info sub_info = { + .complete = &done, + .path = path, + .argv = argv, + .envp = envp, + .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); + +void __init usermodehelper_init(void) +{ + khelper_wq = create_singlethread_workqueue("khelper"); + BUG_ON(!khelper_wq); +} |
