Commit f869e8a7 authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 56007cae

drivers/staging/android/binder.c

+2 −11
Original line number Diff line number Diff line
@@ -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);

}



/*

fs/file.c

+14 −2
Original line number Diff line number Diff line
@@ -599,11 +599,18 @@ EXPORT_SYMBOL(put_unused_fd); 
 *

 * It should never happen - if we allow dup2() do it, _really_ bad things

 * will follow.

 *

 * NOTE: __fd_install() variant is really, really low-level; don't

 * use it unless you are forced to by truly lousy API shoved down

 * your throat.  'files' *MUST* be either current->files or obtained

 * by get_files_struct(current) done by whoever had given it to you,

 * or really bad things will happen.  Normally you want to use

 * fd_install() instead.

 */



void fd_install(unsigned int fd, struct file *file)

void __fd_install(struct files_struct *files, unsigned int fd,

		struct file *file)

{

	struct files_struct *files = current->files;

	struct fdtable *fdt;

	spin_lock(&files->file_lock);

	fdt = files_fdtable(files);
@@ -612,4 +619,9 @@ void fd_install(unsigned int fd, struct file *file) 
	spin_unlock(&files->file_lock);

}



void fd_install(unsigned int fd, struct file *file)

{

	__fd_install(current->files, fd, file);

}



EXPORT_SYMBOL(fd_install);

include/linux/fdtable.h

+2 −0
Original line number Diff line number Diff line
@@ -121,6 +121,8 @@ struct files_struct *dup_fd(struct files_struct *, int *); 


extern int __alloc_fd(struct files_struct *files,

		      unsigned start, unsigned end, unsigned flags);

extern void __fd_install(struct files_struct *files,

		      unsigned int fd, struct file *file);



extern struct kmem_cache *files_cachep;

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