expose a low-level variant of fd_install() for binder

Similar situation to that of __alloc_fd(); do not use unless you
really have to.  You should not touch any descriptor table other
than your own; it's a sure sign of a really bad API design.

As with __alloc_fd(), you *must* use a first-class reference to
struct files_struct; something obtained by get_files_struct(some task)
(let alone direct task->files) will not do.  It must be either
current->files, or obtained by get_files_struct(current) by the
owner of that sucker and given to you.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 11 deletions

diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index 4946d282a35..9e1a98a360d 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -386,17 +386,8 @@ int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
 static void task_fd_install(
         struct binder_proc *proc, unsigned int fd, struct file *file)
 {
-        struct files_struct *files = proc->files;
-        struct fdtable *fdt;
-
-        if (files == NULL)
-                return;
-
-        spin_lock(&files->file_lock);
-        fdt = files_fdtable(files);
-        BUG_ON(fdt->fd[fd] != NULL);
-        rcu_assign_pointer(fdt->fd[fd], file);
-        spin_unlock(&files->file_lock);
+        if (proc->files)
+                __fd_install(proc->files, fd, file);
 }
 
 /*