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>

diff --git a/Documentation/filesystems/files.txt b/Documentation/filesystems/files.txt
index ac2facc..46dfc6b 100644 (file)
--- 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 03c5fce..c2c5b07 100644 (file)
--- 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 094e18c..b667f7e 100644 (file)
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -409,11 +409,11 @@ 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 */
@@ -454,7 +454,7 @@ 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;
 }
@@ -480,7 +480,7 @@ 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 56bac70..1f865c9 100644 (file)
--- 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 3625464..e91f776 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -2073,8 +2073,8 @@ 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 22764c7..75e7c1f 100644 (file)
--- 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 4c6992d..114fea0 100644 (file)
--- 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 33b4033..0434ee9 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -837,7 +837,7 @@ 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;
 }
@@ -1081,7 +1081,7 @@ 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 1ace83d..ed000c1 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1830,7 +1830,7 @@ 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 82163c4..7675da2 100644 (file)
--- 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
  */