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Subject[PATCH 1/3] Wrap accesses to the fd_sets in struct fdtable
Date
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>
---

Documentation/filesystems/files.txt | 4 ++-
arch/powerpc/platforms/cell/spufs/coredump.c | 2 +-
drivers/staging/android/binder.c | 10 ++++-----
fs/autofs4/dev-ioctl.c | 2 +-
fs/exec.c | 4 ++-
fs/fcntl.c | 18 ++++++++--------
fs/file.c | 8 +++----
fs/open.c | 4 ++-
fs/proc/base.c | 2 +-
include/linux/fdtable.h | 30 ++++++++++++++++++++++++++
10 files changed, 57 insertions(+), 27 deletions(-)

diff --git a/Documentation/filesystems/files.txt b/Documentation/filesystems/files.txt
index ac2facc..46dfc6b 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 03c5fce..c2c5b07 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 f0b7e66..347bd6e 100644
--- 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 76741d8..3dfd615 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 92ce83a..22cc38d 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 22764c7..75e7c1f 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 4c6992d..114fea0 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 77becc0..5720854 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 d4548dd..db6ab4b 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 82163c4..7675da2 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
*/


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