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authorPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
committerPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
commit70711d223510ba1773cfe1d7770a56141c815ff8 (patch)
tree4a71f38a3a554ddecaa31b7d8c6bc49b7d1705b4 /fs/file.c
parentd53b4ed072d9779cdf53582c46436dec06d0961f (diff)
parent19f949f52599ba7c3f67a5897ac6be14bfcb1200 (diff)
Merge tag 'v3.8' of /home/kaber/src/repos/linux
Linux 3.8 Signed-off-by: Patrick McHardy <kaber@trash.net> Conflicts: include/linux/Kbuild include/linux/netlink.h
Diffstat (limited to 'fs/file.c')
-rw-r--r--fs/file.c573
1 files changed, 548 insertions, 25 deletions
diff --git a/fs/file.c b/fs/file.c
index ba3f6053025..2b3570b7cae 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;
@@ -395,7 +401,96 @@ out:
return NULL;
}
-static void __devinit fdtable_defer_list_init(int cpu)
+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 fdtable_defer_list_init(int cpu)
{
struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
spin_lock_init(&fddef->lock);
@@ -427,9 +522,9 @@ struct 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 +539,14 @@ 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 +580,428 @@ 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(0, 0);
+ 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)
+{
+ __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 */
+ 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 -EBADF;
+
+ 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 (unlikely(oldfd == newfd))
+ return -EINVAL;
+
+ if (newfd >= rlimit(RLIMIT_NOFILE))
+ return -EBADF;
+
+ 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;
+ int res = 0;
+ if (!files)
+ return 0;
+ spin_lock(&files->file_lock);
+ for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
+ struct file *file;
+ file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
+ if (!file)
+ continue;
+ res = f(p, file, n);
+ if (res)
+ break;
+ }
+ spin_unlock(&files->file_lock);
+ return res;
}
-EXPORT_SYMBOL(get_unused_fd);
+EXPORT_SYMBOL(iterate_fd);