[PATCH] Create call_usermodehelper_pipe()

A new member in the ever growing family of call_usermode* functions is
born.  The new call_usermodehelper_pipe() function allows to pipe data to
the stdin of the called user mode progam and behaves otherwise like the
normal call_usermodehelp() (except that it always waits for the child to
finish)

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 58 insertions, 1 deletions

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 0db22a1ab474..10f505c8431d 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -47,4 +47,8 @@ call_usermodehelper(char *path, char **argv, char **envp, int wait)
 
 extern void usermodehelper_init(void);
 
+struct file;
+extern int call_usermodehelper_pipe(char *path, char *argv[], char *envp[],
+                                    struct file **filp);
+
 #endif /* __LINUX_KMOD_H__ */
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 842f8015d7fd..5c63c53014a9 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -122,6 +122,7 @@ struct subprocess_info {
         struct key *ring;
         int wait;
         int retval;
+        struct file *stdin;
 };
 
 /*
@@ -145,12 +146,26 @@ static int ____call_usermodehelper(void *data)
 
         key_put(old_session);
 
+        /* 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);
+        }
+
         /* 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);
+                retval = execve(sub_info->path, sub_info->argv, sub_info->envp);
 
         /* Exec failed? */
         sub_info->retval = retval;
@@ -268,6 +283,44 @@ int call_usermodehelper_keys(char *path, char **argv, char **envp,
 }
 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");