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![David Howells](/assets/img/avatar_default.png)
The attached patch makes it possible to pass a session keyring through to the process spawned by call_usermodehelper(). This allows patch 3/3 to pass an authorisation key through to /sbin/request-key, thus permitting better access controls when doing just-in-time key creation. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
265 lines
7.6 KiB
C
265 lines
7.6 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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#define __KERNEL_SYSCALLS__
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#include <linux/config.h>
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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/smp_lock.h>
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#include <linux/slab.h>
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#include <linux/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 <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 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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};
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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 *old_session;
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int retval;
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/* Unblock all signals and set the session keyring. */
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key_get(sub_info->ring);
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flush_signals(current);
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spin_lock_irq(¤t->sighand->siglock);
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old_session = __install_session_keyring(current, sub_info->ring);
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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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/* We can run anywhere, unlike our parent keventd(). */
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set_cpus_allowed(current, CPU_MASK_ALL);
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retval = -EPERM;
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if (current->fs->root)
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retval = execve(sub_info->path, 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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struct k_sigaction sa;
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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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sa.sa.sa_handler = SIG_IGN;
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sa.sa.sa_flags = 0;
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siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
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do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
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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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/*
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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 *) &sub_info->retval, 0, NULL);
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}
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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(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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/* 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 (sub_info->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 (pid < 0) {
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sub_info->retval = pid;
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complete(sub_info->complete);
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} else if (!sub_info->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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*
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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(done);
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struct subprocess_info sub_info = {
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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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.ring = session_keyring,
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.wait = wait,
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.retval = 0,
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};
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DECLARE_WORK(work, __call_usermodehelper, &sub_info);
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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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queue_work(khelper_wq, &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_keys);
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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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