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>

10 files changed, 57 insertions, 27 deletions

diff --git a/Documentation/filesystems/files.txt b/Documentation/filesystems/files.txt
index ac2facc50d2a..46dfc6b038c3 100644
--- a/Documentation/filesystems/files.txt
+++ b/Documentation/filesystems/files.txt
@@ -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);
         .....
 
diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c
index 03c5fce2a5b3..c2c5b078ba80 100644
--- a/arch/powerpc/platforms/cell/spufs/coredump.c
+++ b/arch/powerpc/platforms/cell/spufs/coredump.c
@@ -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);
diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index 7491801a661c..35dd9c370e55 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -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);
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 76741d8d7786..3dfd615afb6b 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -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);
 }
 
diff --git a/fs/exec.c b/fs/exec.c
index 92ce83a11e90..22cc38d9e79f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -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 */
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 22764c7c8382..75e7c1f3a080 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -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)
diff --git a/fs/file.c b/fs/file.c
index 4c6992d8f3ba..114fea0a2cec 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -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 */
diff --git a/fs/open.c b/fs/open.c
index 77becc041149..5720854156db 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -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);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d4548dd49b02..db6ab4b36a0b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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) {
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 82163c4b32c9..7675da2c18f7 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -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
  */