From 6319194ec57b0452dcda4589d24c4e7db299c5bf Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 12 May 2022 17:08:03 -0400 Subject: [PATCH] Unify the primitives for file descriptor closing Currently we have 3 primitives for removing an opened file from descriptor table - pick_file(), __close_fd_get_file() and close_fd_get_file(). Their calling conventions are rather odd and there's a code duplication for no good reason. They can be unified - 1) have __range_close() cap max_fd in the very beginning; that way we don't need separate way for pick_file() to report being past the end of descriptor table. 2) make {__,}close_fd_get_file() return file (or NULL) directly, rather than returning it via struct file ** argument. Don't bother with (bogus) return value - nobody wants that -ENOENT. 3) make pick_file() return NULL on unopened descriptor - the only caller that used to care about the distinction between descriptor past the end of descriptor table and finding NULL in descriptor table doesn't give a damn after (1). 4) lift ->files_lock out of pick_file() That actually simplifies the callers, as well as the primitives themselves. Code duplication is also gone... Reviewed-by: Christian Brauner (Microsoft) Signed-off-by: Al Viro --- drivers/android/binder.c | 2 +- fs/file.c | 77 +++++++++++++++------------------------- fs/internal.h | 2 +- fs/io_uring.c | 7 ++-- include/linux/fdtable.h | 2 +- 5 files changed, 34 insertions(+), 56 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 8351c5638880..27c9b004823a 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -1855,7 +1855,7 @@ static void binder_deferred_fd_close(int fd) if (!twcb) return; init_task_work(&twcb->twork, binder_do_fd_close); - close_fd_get_file(fd, &twcb->file); + twcb->file = close_fd_get_file(fd); if (twcb->file) { filp_close(twcb->file, current->files); task_work_add(current, &twcb->twork, TWA_RESUME); diff --git a/fs/file.c b/fs/file.c index 4c59f410a48d..dd6692048f4f 100644 --- a/fs/file.c +++ b/fs/file.c @@ -630,32 +630,23 @@ EXPORT_SYMBOL(fd_install); * @files: file struct to retrieve file from * @fd: file descriptor to retrieve file for * - * If this functions returns an EINVAL error pointer the fd was beyond the - * current maximum number of file descriptors for that fdtable. + * Context: files_lock must be held. * - * Returns: The file associated with @fd, on error returns an error pointer. + * Returns: The file associated with @fd (NULL if @fd is not open) */ static struct file *pick_file(struct files_struct *files, unsigned fd) { + struct fdtable *fdt = files_fdtable(files); struct file *file; - struct fdtable *fdt; - spin_lock(&files->file_lock); - fdt = files_fdtable(files); - if (fd >= fdt->max_fds) { - file = ERR_PTR(-EINVAL); - goto out_unlock; - } + if (fd >= fdt->max_fds) + return NULL; + file = fdt->fd[fd]; - if (!file) { - file = ERR_PTR(-EBADF); - goto out_unlock; + if (file) { + rcu_assign_pointer(fdt->fd[fd], NULL); + __put_unused_fd(files, fd); } - rcu_assign_pointer(fdt->fd[fd], NULL); - __put_unused_fd(files, fd); - -out_unlock: - spin_unlock(&files->file_lock); return file; } @@ -664,8 +655,10 @@ int close_fd(unsigned fd) struct files_struct *files = current->files; struct file *file; + spin_lock(&files->file_lock); file = pick_file(files, fd); - if (IS_ERR(file)) + spin_unlock(&files->file_lock); + if (!file) return -EBADF; return filp_close(file, files); @@ -702,20 +695,25 @@ static inline void __range_cloexec(struct files_struct *cur_fds, static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, unsigned int max_fd) { + unsigned n; + + rcu_read_lock(); + n = last_fd(files_fdtable(cur_fds)); + rcu_read_unlock(); + max_fd = min(max_fd, n); + while (fd <= max_fd) { struct file *file; + spin_lock(&cur_fds->file_lock); file = pick_file(cur_fds, fd++); - if (!IS_ERR(file)) { + spin_unlock(&cur_fds->file_lock); + + if (file) { /* found a valid file to close */ filp_close(file, cur_fds); cond_resched(); - continue; } - - /* beyond the last fd in that table */ - if (PTR_ERR(file) == -EINVAL) - return; } } @@ -795,26 +793,9 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) * See close_fd_get_file() below, this variant assumes current->files->file_lock * is held. */ -int __close_fd_get_file(unsigned int fd, struct file **res) +struct file *__close_fd_get_file(unsigned int fd) { - struct files_struct *files = current->files; - struct file *file; - struct fdtable *fdt; - - fdt = files_fdtable(files); - if (fd >= fdt->max_fds) - goto out_err; - file = fdt->fd[fd]; - if (!file) - goto out_err; - rcu_assign_pointer(fdt->fd[fd], NULL); - __put_unused_fd(files, fd); - get_file(file); - *res = file; - return 0; -out_err: - *res = NULL; - return -ENOENT; + return pick_file(current->files, fd); } /* @@ -822,16 +803,16 @@ out_err: * The caller must ensure that filp_close() called on the file, and then * an fput(). */ -int close_fd_get_file(unsigned int fd, struct file **res) +struct file *close_fd_get_file(unsigned int fd) { struct files_struct *files = current->files; - int ret; + struct file *file; spin_lock(&files->file_lock); - ret = __close_fd_get_file(fd, res); + file = pick_file(files, fd); spin_unlock(&files->file_lock); - return ret; + return file; } void do_close_on_exec(struct files_struct *files) diff --git a/fs/internal.h b/fs/internal.h index 08503dc68d2b..4065e2679103 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -125,7 +125,7 @@ extern struct file *do_file_open_root(const struct path *, const char *, const struct open_flags *); extern struct open_how build_open_how(int flags, umode_t mode); extern int build_open_flags(const struct open_how *how, struct open_flags *op); -extern int __close_fd_get_file(unsigned int fd, struct file **res); +extern struct file *__close_fd_get_file(unsigned int fd); long do_sys_ftruncate(unsigned int fd, loff_t length, int small); int chmod_common(const struct path *path, umode_t mode); diff --git a/fs/io_uring.c b/fs/io_uring.c index dc580a30723d..7257b0870353 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5137,13 +5137,10 @@ static int io_close(struct io_kiocb *req, unsigned int issue_flags) return -EAGAIN; } - ret = __close_fd_get_file(close->fd, &file); + file = __close_fd_get_file(close->fd); spin_unlock(&files->file_lock); - if (ret < 0) { - if (ret == -ENOENT) - ret = -EBADF; + if (!file) goto err; - } /* No ->flush() or already async, safely close from here */ ret = filp_close(file, current->files); diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index d0e78174874a..e066816f3519 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -125,7 +125,7 @@ int iterate_fd(struct files_struct *, unsigned, extern int close_fd(unsigned int fd); extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags); -extern int close_fd_get_file(unsigned int fd, struct file **res); +extern struct file *close_fd_get_file(unsigned int fd); extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, struct files_struct **new_fdp);