1 files changed, 549 insertions, 24 deletions

diff --git a/fs/file.c b/fs/file.c
index ba3f6053025c..0f1bda4bebfa 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -6,6 +6,7 @@
  *  Manage the dynamic fd arrays in the process files_struct.
  */
 
+#include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
@@ -84,22 +85,14 @@ static void free_fdtable_work(struct work_struct *work)
         }
 }
 
-void free_fdtable_rcu(struct rcu_head *rcu)
+static void free_fdtable_rcu(struct rcu_head *rcu)
 {
         struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
         struct fdtable_defer *fddef;
 
         BUG_ON(!fdt);
+        BUG_ON(fdt->max_fds <= NR_OPEN_DEFAULT);
 
-        if (fdt->max_fds <= NR_OPEN_DEFAULT) {
-                /*
-                 * This fdtable is embedded in the files structure and that
-                 * structure itself is getting destroyed.
-                 */
-                kmem_cache_free(files_cachep,
-                                container_of(fdt, struct files_struct, fdtab));
-                return;
-        }
         if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
                 kfree(fdt->fd);
                 kfree(fdt->open_fds);
@@ -229,7 +222,7 @@ static int expand_fdtable(struct files_struct *files, int nr)
                 copy_fdtable(new_fdt, cur_fdt);
                 rcu_assign_pointer(files->fdt, new_fdt);
                 if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
-                        free_fdtable(cur_fdt);
+                        call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
         } else {
                 /* Somebody else expanded, so undo our attempt */
                 __free_fdtable(new_fdt);
@@ -245,19 +238,12 @@ static int expand_fdtable(struct files_struct *files, int nr)
  * expanded and execution may have blocked.
  * The files->file_lock should be held on entry, and will be held on exit.
  */
-int expand_files(struct files_struct *files, int nr)
+static int expand_files(struct files_struct *files, int nr)
 {
         struct fdtable *fdt;
 
         fdt = files_fdtable(files);
 
-        /*
-         * N.B. For clone tasks sharing a files structure, this test
-         * will limit the total number of files that can be opened.
-         */
-        if (nr >= rlimit(RLIMIT_NOFILE))
-                return -EMFILE;
-
         /* Do we need to expand? */
         if (nr < fdt->max_fds)
                 return 0;
@@ -270,6 +256,26 @@ int expand_files(struct files_struct *files, int nr)
         return expand_fdtable(files, nr);
 }
 
+static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
+{
+        __set_bit(fd, fdt->close_on_exec);
+}
+
+static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
+{
+        __clear_bit(fd, fdt->close_on_exec);
+}
+
+static inline void __set_open_fd(int fd, struct fdtable *fdt)
+{
+        __set_bit(fd, fdt->open_fds);
+}
+
+static inline void __clear_open_fd(int fd, struct fdtable *fdt)
+{
+        __clear_bit(fd, fdt->open_fds);
+}
+
 static int count_open_files(struct fdtable *fdt)
 {
         int size = fdt->max_fds;
@@ -395,6 +401,95 @@ out:
         return NULL;
 }
 
+static void close_files(struct files_struct * files)
+{
+        int i, j;
+        struct fdtable *fdt;
+
+        j = 0;
+
+        /*
+         * It is safe to dereference the fd table without RCU or
+         * ->file_lock because this is the last reference to the
+         * files structure.  But use RCU to shut RCU-lockdep up.
+         */
+        rcu_read_lock();
+        fdt = files_fdtable(files);
+        rcu_read_unlock();
+        for (;;) {
+                unsigned long set;
+                i = j * BITS_PER_LONG;
+                if (i >= fdt->max_fds)
+                        break;
+                set = fdt->open_fds[j++];
+                while (set) {
+                        if (set & 1) {
+                                struct file * file = xchg(&fdt->fd[i], NULL);
+                                if (file) {
+                                        filp_close(file, files);
+                                        cond_resched();
+                                }
+                        }
+                        i++;
+                        set >>= 1;
+                }
+        }
+}
+
+struct files_struct *get_files_struct(struct task_struct *task)
+{
+        struct files_struct *files;
+
+        task_lock(task);
+        files = task->files;
+        if (files)
+                atomic_inc(&files->count);
+        task_unlock(task);
+
+        return files;
+}
+
+void put_files_struct(struct files_struct *files)
+{
+        struct fdtable *fdt;
+
+        if (atomic_dec_and_test(&files->count)) {
+                close_files(files);
+                /* not really needed, since nobody can see us */
+                rcu_read_lock();
+                fdt = files_fdtable(files);
+                rcu_read_unlock();
+                /* free the arrays if they are not embedded */
+                if (fdt != &files->fdtab)
+                        __free_fdtable(fdt);
+                kmem_cache_free(files_cachep, files);
+        }
+}
+
+void reset_files_struct(struct files_struct *files)
+{
+        struct task_struct *tsk = current;
+        struct files_struct *old;
+
+        old = tsk->files;
+        task_lock(tsk);
+        tsk->files = files;
+        task_unlock(tsk);
+        put_files_struct(old);
+}
+
+void exit_files(struct task_struct *tsk)
+{
+        struct files_struct * files = tsk->files;
+
+        if (files) {
+                task_lock(tsk);
+                tsk->files = NULL;
+                task_unlock(tsk);
+                put_files_struct(files);
+        }
+}
+
 static void __devinit fdtable_defer_list_init(int cpu)
 {
         struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
@@ -424,12 +519,18 @@ struct files_struct init_files = {
         .file_lock      = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
 };
 
+void daemonize_descriptors(void)
+{
+        atomic_inc(&init_files.count);
+        reset_files_struct(&init_files);
+}
+
 /*
  * allocate a file descriptor, mark it busy.
  */
-int alloc_fd(unsigned start, unsigned flags)
+int __alloc_fd(struct files_struct *files,
+               unsigned start, unsigned end, unsigned flags)
 {
-        struct files_struct *files = current->files;
         unsigned int fd;
         int error;
         struct fdtable *fdt;
@@ -444,6 +545,14 @@ repeat:
         if (fd < fdt->max_fds)
                 fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
 
+        /*
+         * N.B. For clone tasks sharing a files structure, this test
+         * will limit the total number of files that can be opened.
+         */
+        error = -EMFILE;
+        if (fd >= end)
+                goto out;
+
         error = expand_files(files, fd);
         if (error < 0)
                 goto out;
@@ -477,8 +586,424 @@ out:
         return error;
 }
 
-int get_unused_fd(void)
+static int alloc_fd(unsigned start, unsigned flags)
+{
+        return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
+}
+
+int get_unused_fd_flags(unsigned flags)
+{
+        return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
+}
+EXPORT_SYMBOL(get_unused_fd_flags);
+
+static void __put_unused_fd(struct files_struct *files, unsigned int fd)
+{
+        struct fdtable *fdt = files_fdtable(files);
+        __clear_open_fd(fd, fdt);
+        if (fd < files->next_fd)
+                files->next_fd = fd;
+}
+
+void put_unused_fd(unsigned int fd)
+{
+        struct files_struct *files = current->files;
+        spin_lock(&files->file_lock);
+        __put_unused_fd(files, fd);
+        spin_unlock(&files->file_lock);
+}
+
+EXPORT_SYMBOL(put_unused_fd);
+
+/*
+ * Install a file pointer in the fd array.
+ *
+ * The VFS is full of places where we drop the files lock between
+ * setting the open_fds bitmap and installing the file in the file
+ * array.  At any such point, we are vulnerable to a dup2() race
+ * installing a file in the array before us.  We need to detect this and
+ * fput() the struct file we are about to overwrite in this case.
+ *
+ * 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(struct files_struct *files, unsigned int fd,
+                struct file *file)
+{
+        struct fdtable *fdt;
+        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);
+}
+
+void fd_install(unsigned int fd, struct file *file)
 {
-        return alloc_fd(0, 0);
+        __fd_install(current->files, fd, file);
+}
+
+EXPORT_SYMBOL(fd_install);
+
+/*
+ * The same warnings as for __alloc_fd()/__fd_install() apply here...
+ */
+int __close_fd(struct files_struct *files, unsigned fd)
+{
+        struct file *file;
+        struct fdtable *fdt;
+
+        spin_lock(&files->file_lock);
+        fdt = files_fdtable(files);
+        if (fd >= fdt->max_fds)
+                goto out_unlock;
+        file = fdt->fd[fd];
+        if (!file)
+                goto out_unlock;
+        rcu_assign_pointer(fdt->fd[fd], NULL);
+        __clear_close_on_exec(fd, fdt);
+        __put_unused_fd(files, fd);
+        spin_unlock(&files->file_lock);
+        return filp_close(file, files);
+
+out_unlock:
+        spin_unlock(&files->file_lock);
+        return -EBADF;
+}
+
+void do_close_on_exec(struct files_struct *files)
+{
+        unsigned i;
+        struct fdtable *fdt;
+
+        /* exec unshares first */
+        BUG_ON(atomic_read(&files->count) != 1);
+        spin_lock(&files->file_lock);
+        for (i = 0; ; i++) {
+                unsigned long set;
+                unsigned fd = i * BITS_PER_LONG;
+                fdt = files_fdtable(files);
+                if (fd >= fdt->max_fds)
+                        break;
+                set = fdt->close_on_exec[i];
+                if (!set)
+                        continue;
+                fdt->close_on_exec[i] = 0;
+                for ( ; set ; fd++, set >>= 1) {
+                        struct file *file;
+                        if (!(set & 1))
+                                continue;
+                        file = fdt->fd[fd];
+                        if (!file)
+                                continue;
+                        rcu_assign_pointer(fdt->fd[fd], NULL);
+                        __put_unused_fd(files, fd);
+                        spin_unlock(&files->file_lock);
+                        filp_close(file, files);
+                        cond_resched();
+                        spin_lock(&files->file_lock);
+                }
+
+        }
+        spin_unlock(&files->file_lock);
+}
+
+struct file *fget(unsigned int fd)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        rcu_read_lock();
+        file = fcheck_files(files, fd);
+        if (file) {
+                /* File object ref couldn't be taken */
+                if (file->f_mode & FMODE_PATH ||
+                    !atomic_long_inc_not_zero(&file->f_count))
+                        file = NULL;
+        }
+        rcu_read_unlock();
+
+        return file;
+}
+
+EXPORT_SYMBOL(fget);
+
+struct file *fget_raw(unsigned int fd)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        rcu_read_lock();
+        file = fcheck_files(files, fd);
+        if (file) {
+                /* File object ref couldn't be taken */
+                if (!atomic_long_inc_not_zero(&file->f_count))
+                        file = NULL;
+        }
+        rcu_read_unlock();
+
+        return file;
+}
+
+EXPORT_SYMBOL(fget_raw);
+
+/*
+ * Lightweight file lookup - no refcnt increment if fd table isn't shared.
+ *
+ * You can use this instead of fget if you satisfy all of the following
+ * conditions:
+ * 1) You must call fput_light before exiting the syscall and returning control
+ *    to userspace (i.e. you cannot remember the returned struct file * after
+ *    returning to userspace).
+ * 2) You must not call filp_close on the returned struct file * in between
+ *    calls to fget_light and fput_light.
+ * 3) You must not clone the current task in between the calls to fget_light
+ *    and fput_light.
+ *
+ * The fput_needed flag returned by fget_light should be passed to the
+ * corresponding fput_light.
+ */
+struct file *fget_light(unsigned int fd, int *fput_needed)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        *fput_needed = 0;
+        if (atomic_read(&files->count) == 1) {
+                file = fcheck_files(files, fd);
+                if (file && (file->f_mode & FMODE_PATH))
+                        file = NULL;
+        } else {
+                rcu_read_lock();
+                file = fcheck_files(files, fd);
+                if (file) {
+                        if (!(file->f_mode & FMODE_PATH) &&
+                            atomic_long_inc_not_zero(&file->f_count))
+                                *fput_needed = 1;
+                        else
+                                /* Didn't get the reference, someone's freed */
+                                file = NULL;
+                }
+                rcu_read_unlock();
+        }
+
+        return file;
+}
+EXPORT_SYMBOL(fget_light);
+
+struct file *fget_raw_light(unsigned int fd, int *fput_needed)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        *fput_needed = 0;
+        if (atomic_read(&files->count) == 1) {
+                file = fcheck_files(files, fd);
+        } else {
+                rcu_read_lock();
+                file = fcheck_files(files, fd);
+                if (file) {
+                        if (atomic_long_inc_not_zero(&file->f_count))
+                                *fput_needed = 1;
+                        else
+                                /* Didn't get the reference, someone's freed */
+                                file = NULL;
+                }
+                rcu_read_unlock();
+        }
+
+        return file;
+}
+
+void set_close_on_exec(unsigned int fd, int flag)
+{
+        struct files_struct *files = current->files;
+        struct fdtable *fdt;
+        spin_lock(&files->file_lock);
+        fdt = files_fdtable(files);
+        if (flag)
+                __set_close_on_exec(fd, fdt);
+        else
+                __clear_close_on_exec(fd, fdt);
+        spin_unlock(&files->file_lock);
+}
+
+bool get_close_on_exec(unsigned int fd)
+{
+        struct files_struct *files = current->files;
+        struct fdtable *fdt;
+        bool res;
+        rcu_read_lock();
+        fdt = files_fdtable(files);
+        res = close_on_exec(fd, fdt);
+        rcu_read_unlock();
+        return res;
+}
+
+static int do_dup2(struct files_struct *files,
+        struct file *file, unsigned fd, unsigned flags)
+{
+        struct file *tofree;
+        struct fdtable *fdt;
+
+        /*
+         * We need to detect attempts to do dup2() over allocated but still
+         * not finished descriptor.  NB: OpenBSD avoids that at the price of
+         * extra work in their equivalent of fget() - they insert struct
+         * file immediately after grabbing descriptor, mark it larval if
+         * more work (e.g. actual opening) is needed and make sure that
+         * fget() treats larval files as absent.  Potentially interesting,
+         * but while extra work in fget() is trivial, locking implications
+         * and amount of surgery on open()-related paths in VFS are not.
+         * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
+         * deadlocks in rather amusing ways, AFAICS.  All of that is out of
+         * scope of POSIX or SUS, since neither considers shared descriptor
+         * tables and this condition does not arise without those.
+         */
+        fdt = files_fdtable(files);
+        tofree = fdt->fd[fd];
+        if (!tofree && fd_is_open(fd, fdt))
+                goto Ebusy;
+        get_file(file);
+        rcu_assign_pointer(fdt->fd[fd], file);
+        __set_open_fd(fd, fdt);
+        if (flags & O_CLOEXEC)
+                __set_close_on_exec(fd, fdt);
+        else
+                __clear_close_on_exec(fd, fdt);
+        spin_unlock(&files->file_lock);
+
+        if (tofree)
+                filp_close(tofree, files);
+
+        return fd;
+
+Ebusy:
+        spin_unlock(&files->file_lock);
+        return -EBUSY;
+}
+
+int replace_fd(unsigned fd, struct file *file, unsigned flags)
+{
+        int err;
+        struct files_struct *files = current->files;
+
+        if (!file)
+                return __close_fd(files, fd);
+
+        if (fd >= rlimit(RLIMIT_NOFILE))
+                return -EMFILE;
+
+        spin_lock(&files->file_lock);
+        err = expand_files(files, fd);
+        if (unlikely(err < 0))
+                goto out_unlock;
+        return do_dup2(files, file, fd, flags);
+
+out_unlock:
+        spin_unlock(&files->file_lock);
+        return err;
+}
+
+SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
+{
+        int err = -EBADF;
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        if ((flags & ~O_CLOEXEC) != 0)
+                return -EINVAL;
+
+        if (newfd >= rlimit(RLIMIT_NOFILE))
+                return -EMFILE;
+
+        spin_lock(&files->file_lock);
+        err = expand_files(files, newfd);
+        file = fcheck(oldfd);
+        if (unlikely(!file))
+                goto Ebadf;
+        if (unlikely(err < 0)) {
+                if (err == -EMFILE)
+                        goto Ebadf;
+                goto out_unlock;
+        }
+        return do_dup2(files, file, newfd, flags);
+
+Ebadf:
+        err = -EBADF;
+out_unlock:
+        spin_unlock(&files->file_lock);
+        return err;
+}
+
+SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
+{
+        if (unlikely(newfd == oldfd)) { /* corner case */
+                struct files_struct *files = current->files;
+                int retval = oldfd;
+
+                rcu_read_lock();
+                if (!fcheck_files(files, oldfd))
+                        retval = -EBADF;
+                rcu_read_unlock();
+                return retval;
+        }
+        return sys_dup3(oldfd, newfd, 0);
+}
+
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
+{
+        int ret = -EBADF;
+        struct file *file = fget_raw(fildes);
+
+        if (file) {
+                ret = get_unused_fd();
+                if (ret >= 0)
+                        fd_install(ret, file);
+                else
+                        fput(file);
+        }
+        return ret;
+}
+
+int f_dupfd(unsigned int from, struct file *file, unsigned flags)
+{
+        int err;
+        if (from >= rlimit(RLIMIT_NOFILE))
+                return -EINVAL;
+        err = alloc_fd(from, flags);
+        if (err >= 0) {
+                get_file(file);
+                fd_install(err, file);
+        }
+        return err;
+}
+
+int iterate_fd(struct files_struct *files, unsigned n,
+                int (*f)(const void *, struct file *, unsigned),
+                const void *p)
+{
+        struct fdtable *fdt;
+        struct file *file;
+        int res = 0;
+        if (!files)
+                return 0;
+        spin_lock(&files->file_lock);
+        fdt = files_fdtable(files);
+        while (!res && n < fdt->max_fds) {
+                file = rcu_dereference_check_fdtable(files, fdt->fd[n++]);
+                if (file)
+                        res = f(p, file, n);
+        }
+        spin_unlock(&files->file_lock);
+        return res;
 }
-EXPORT_SYMBOL(get_unused_fd);
+EXPORT_SYMBOL(iterate_fd);