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Wrap accesses to the fd_sets in struct fdtable 

Wrap accesses to the fd_sets in struct fdtable (for recording open files and
close-on-exec flags) so that we can move away from using fd_sets since we
abuse the fd_set structs by not allocating the full-sized structure under
normal circumstances and by non-core code looking at the internals of the
fd_sets.

The first abuse means that use of FD_ZERO() on these fd_sets is not permitted,
since that cannot be told about their abnormal lengths.

This introduces six wrapper functions for setting, clearing and testing
close-on-exec flags and fd-is-open flags:

	void __set_close_on_exec(int fd, struct fdtable *fdt);
	void __clear_close_on_exec(int fd, struct fdtable *fdt);
	bool close_on_exec(int fd, const struct fdtable *fdt);
	void __set_open_fd(int fd, struct fdtable *fdt);
	void __clear_open_fd(int fd, struct fdtable *fdt);
	bool fd_is_open(int fd, const struct fdtable *fdt);

Note that I've prepended '__' to the names of the set/clear functions because
they require the caller to hold a lock to use them.

Note also that I haven't added wrappers for looking behind the scenes at the
the array.  Possibly that should exist too.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120216174942.23314.1364.stgit@warthog.procyon.org.uk
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
David Howells 2012-02-16 17:49:42 +00:00 committed by H. Peter Anvin
parent 8b3d1cda4f
commit 1dce27c5aa
10 changed files with 57 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/filesystems/files.txt
View File

@ -113,8 +113,8 @@ the fdtable structure -
if (fd >= 0) {
/* locate_fd() may have expanded fdtable, load the ptr */
fdt = files_fdtable(files);
FD_SET(fd, fdt->open_fds);
FD_CLR(fd, fdt->close_on_exec);
__set_open_fd(fd, fdt);
__clear_close_on_exec(fd, fdt);
spin_unlock(&files->file_lock);
.....

2
arch/powerpc/platforms/cell/spufs/coredump.c
View File

@ -122,7 +122,7 @@ static struct spu_context *coredump_next_context(int *fd)
struct spu_context *ctx = NULL;
for (; *fd < fdt->max_fds; (*fd)++) {
if (!FD_ISSET(*fd, fdt->open_fds))
if (!fd_is_open(*fd, fdt))
continue;
file = fcheck(*fd);

10
drivers/staging/android/binder.c
View File

@ -408,11 +408,11 @@ repeat:
goto repeat;
}
FD_SET(fd, fdt->open_fds);
__set_open_fd(fd, fdt);
if (flags & O_CLOEXEC)
FD_SET(fd, fdt->close_on_exec);
__set_close_on_exec(fd, fdt);
else
FD_CLR(fd, fdt->close_on_exec);
__clear_close_on_exec(fd, fdt);
files->next_fd = fd + 1;
#if 1
/* Sanity check */
@ -453,7 +453,7 @@ static void task_fd_install(
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = files_fdtable(files);
__FD_CLR(fd, fdt->open_fds);
__clear_open_fd(fd, fdt);
if (fd < files->next_fd)
files->next_fd = fd;
}
@ -479,7 +479,7 @@ static long task_close_fd(struct binder_proc *proc, unsigned int fd)
if (!filp)
goto out_unlock;
rcu_assign_pointer(fdt->fd[fd], NULL);
FD_CLR(fd, fdt->close_on_exec);
__clear_close_on_exec(fd, fdt);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
retval = filp_close(filp, files);

2
fs/autofs4/dev-ioctl.c
View File

@ -230,7 +230,7 @@ static void autofs_dev_ioctl_fd_install(unsigned int fd, struct file *file)
fdt = files_fdtable(files);
BUG_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
FD_SET(fd, fdt->close_on_exec);
__set_close_on_exec(fd, fdt);
spin_unlock(&files->file_lock);
}

4
fs/exec.c
View File

@ -2078,8 +2078,8 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
fd_install(0, rp);
spin_lock(&cf->file_lock);
fdt = files_fdtable(cf);
FD_SET(0, fdt->open_fds);
FD_CLR(0, fdt->close_on_exec);
__set_open_fd(0, fdt);
__clear_close_on_exec(0, fdt);
spin_unlock(&cf->file_lock);
/* and disallow core files too */

18
fs/fcntl.c
View File

@ -32,20 +32,20 @@ void set_close_on_exec(unsigned int fd, int flag)
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
if (flag)
FD_SET(fd, fdt->close_on_exec);
__set_close_on_exec(fd, fdt);
else
FD_CLR(fd, fdt->close_on_exec);
__clear_close_on_exec(fd, fdt);
spin_unlock(&files->file_lock);
}
static int get_close_on_exec(unsigned int fd)
static bool get_close_on_exec(unsigned int fd)
{
struct files_struct *files = current->files;
struct fdtable *fdt;
int res;
bool res;
rcu_read_lock();
fdt = files_fdtable(files);
res = FD_ISSET(fd, fdt->close_on_exec);
res = close_on_exec(fd, fdt);
rcu_read_unlock();
return res;
}
@ -90,15 +90,15 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
err = -EBUSY;
fdt = files_fdtable(files);
tofree = fdt->fd[newfd];
if (!tofree && FD_ISSET(newfd, fdt->open_fds))
if (!tofree && fd_is_open(newfd, fdt))
goto out_unlock;
get_file(file);
rcu_assign_pointer(fdt->fd[newfd], file);
FD_SET(newfd, fdt->open_fds);
__set_open_fd(newfd, fdt);
if (flags & O_CLOEXEC)
FD_SET(newfd, fdt->close_on_exec);
__set_close_on_exec(newfd, fdt);
else
FD_CLR(newfd, fdt->close_on_exec);
__clear_close_on_exec(newfd, fdt);
spin_unlock(&files->file_lock);
if (tofree)

8
fs/file.c
View File

@ -366,7 +366,7 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
* is partway through open(). So make sure that this
* fd is available to the new process.
*/
FD_CLR(open_files - i, new_fdt->open_fds);
__clear_open_fd(open_files - i, new_fdt);
}
rcu_assign_pointer(*new_fds++, f);
}
@ -460,11 +460,11 @@ repeat:
if (start <= files->next_fd)
files->next_fd = fd + 1;
FD_SET(fd, fdt->open_fds);
__set_open_fd(fd, fdt);
if (flags & O_CLOEXEC)
FD_SET(fd, fdt->close_on_exec);
__set_close_on_exec(fd, fdt);
else
FD_CLR(fd, fdt->close_on_exec);
__clear_close_on_exec(fd, fdt);
error = fd;
#if 1
/* Sanity check */

4
fs/open.c
View File

@ -836,7 +836,7 @@ EXPORT_SYMBOL(dentry_open);
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = files_fdtable(files);
__FD_CLR(fd, fdt->open_fds);
__clear_open_fd(fd, fdt);
if (fd < files->next_fd)
files->next_fd = fd;
}
@ -1080,7 +1080,7 @@ SYSCALL_DEFINE1(close, unsigned int, fd)
if (!filp)
goto out_unlock;
rcu_assign_pointer(fdt->fd[fd], NULL);
FD_CLR(fd, fdt->close_on_exec);
__clear_close_on_exec(fd, fdt);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
retval = filp_close(filp, files);

2
fs/proc/base.c
View File

@ -1754,7 +1754,7 @@ static int proc_fd_info(struct inode *inode, struct path *path, char *info)
fdt = files_fdtable(files);
f_flags = file->f_flags & ~O_CLOEXEC;
if (FD_ISSET(fd, fdt->close_on_exec))
if (close_on_exec(fd, fdt))
f_flags |= O_CLOEXEC;
if (path) {

30
include/linux/fdtable.h
View File

@ -38,6 +38,36 @@ struct fdtable {
struct fdtable *next;
};
static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
{
FD_SET(fd, fdt->close_on_exec);
}
static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
{
FD_CLR(fd, fdt->close_on_exec);
}
static inline bool close_on_exec(int fd, const struct fdtable *fdt)
{
return FD_ISSET(fd, fdt->close_on_exec);
}
static inline void __set_open_fd(int fd, struct fdtable *fdt)
{
FD_SET(fd, fdt->open_fds);
}
static inline void __clear_open_fd(int fd, struct fdtable *fdt)
{
FD_CLR(fd, fdt->open_fds);
}
static inline bool fd_is_open(int fd, const struct fdtable *fdt)
{
return FD_ISSET(fd, fdt->open_fds);
}
/*
* Open file table structure
*/