1 files changed, 187 insertions, 43 deletions

diff --git a/include/linux/file.h b/include/linux/file.h
index 39704eae83e2..cf389fde9bc2 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -10,6 +10,8 @@
 #include <linux/types.h>
 #include <linux/posix_types.h>
 #include <linux/errno.h>
+#include <linux/cleanup.h>
+#include <linux/err.h>
 
 struct file;
 
@@ -23,63 +25,65 @@ struct inode;
 struct path;
 extern struct file *alloc_file_pseudo(struct inode *, struct vfsmount *,
 	const char *, int flags, const struct file_operations *);
+extern struct file *alloc_file_pseudo_noaccount(struct inode *, struct vfsmount *,
+	const char *, int flags, const struct file_operations *);
 extern struct file *alloc_file_clone(struct file *, int flags,
 	const struct file_operations *);
 
-static inline void fput_light(struct file *file, int fput_needed)
-{
-	if (fput_needed)
-		fput(file);
-}
-
+/* either a reference to struct file + flags
+ * (cloned vs. borrowed, pos locked), with
+ * flags stored in lower bits of value,
+ * or empty (represented by 0).
+ */
 struct fd {
-	struct file *file;
-	unsigned int flags;
+	unsigned long word;
 };
 #define FDPUT_FPUT       1
 #define FDPUT_POS_UNLOCK 2
 
-static inline void fdput(struct fd fd)
+#define fd_file(f) ((struct file *)((f).word & ~(FDPUT_FPUT|FDPUT_POS_UNLOCK)))
+static inline bool fd_empty(struct fd f)
 {
-	if (fd.flags & FDPUT_FPUT)
-		fput(fd.file);
+	return unlikely(!f.word);
 }
 
-extern struct file *fget(unsigned int fd);
-extern struct file *fget_raw(unsigned int fd);
-extern struct file *fget_task(struct task_struct *task, unsigned int fd);
-extern unsigned long __fdget(unsigned int fd);
-extern unsigned long __fdget_raw(unsigned int fd);
-extern unsigned long __fdget_pos(unsigned int fd);
-extern void __f_unlock_pos(struct file *);
-
-static inline struct fd __to_fd(unsigned long v)
+#define EMPTY_FD (struct fd){0}
+static inline struct fd BORROWED_FD(struct file *f)
 {
-	return (struct fd){(struct file *)(v & ~3),v & 3};
+	return (struct fd){(unsigned long)f};
 }
-
-static inline struct fd fdget(unsigned int fd)
+static inline struct fd CLONED_FD(struct file *f)
 {
-	return __to_fd(__fdget(fd));
+	return (struct fd){(unsigned long)f | FDPUT_FPUT};
 }
 
-static inline struct fd fdget_raw(unsigned int fd)
+static inline void fdput(struct fd fd)
 {
-	return __to_fd(__fdget_raw(fd));
+	if (unlikely(fd.word & FDPUT_FPUT))
+		fput(fd_file(fd));
 }
 
-static inline struct fd fdget_pos(int fd)
-{
-	return __to_fd(__fdget_pos(fd));
-}
+extern struct file *fget(unsigned int fd);
+extern struct file *fget_raw(unsigned int fd);
+extern struct file *fget_task(struct task_struct *task, unsigned int fd);
+extern struct file *fget_task_next(struct task_struct *task, unsigned int *fd);
+extern void __f_unlock_pos(struct file *);
+
+struct fd fdget(unsigned int fd);
+struct fd fdget_raw(unsigned int fd);
+struct fd fdget_pos(unsigned int fd);
 
 static inline void fdput_pos(struct fd f)
 {
-	if (f.flags & FDPUT_POS_UNLOCK)
-		__f_unlock_pos(f.file);
+	if (f.word & FDPUT_POS_UNLOCK)
+		__f_unlock_pos(fd_file(f));
 	fdput(f);
 }
 
+DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)
+DEFINE_CLASS(fd_raw, struct fd, fdput(_T), fdget_raw(fd), int fd)
+DEFINE_CLASS(fd_pos, struct fd, fdput_pos(_T), fdget_pos(fd), int fd)
+
 extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
 extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
 extern void set_close_on_exec(unsigned int fd, int flag);
@@ -88,20 +92,34 @@ extern int __get_unused_fd_flags(unsigned flags, unsigned long nofile);
 extern int get_unused_fd_flags(unsigned flags);
 extern void put_unused_fd(unsigned int fd);
 
-extern void fd_install(unsigned int fd, struct file *file);
+DEFINE_CLASS(get_unused_fd, int, if (_T >= 0) put_unused_fd(_T),
+	     get_unused_fd_flags(flags), unsigned flags)
+DEFINE_FREE(fput, struct file *, if (!IS_ERR_OR_NULL(_T)) fput(_T))
 
-extern int __receive_fd(struct file *file, int __user *ufd,
-			unsigned int o_flags);
+/*
+ * take_fd() will take care to set @fd to -EBADF ensuring that
+ * CLASS(get_unused_fd) won't call put_unused_fd(). This makes it
+ * easier to rely on CLASS(get_unused_fd):
+ *
+ * struct file *f;
+ *
+ * CLASS(get_unused_fd, fd)(O_CLOEXEC);
+ * if (fd < 0)
+ *         return fd;
+ *
+ * f = dentry_open(&path, O_RDONLY, current_cred());
+ * if (IS_ERR(f))
+ *         return PTR_ERR(f);
+ *
+ * fd_install(fd, f);
+ * return take_fd(fd);
+ */
+#define take_fd(fd) __get_and_null(fd, -EBADF)
 
-extern int receive_fd(struct file *file, unsigned int o_flags);
+extern void fd_install(unsigned int fd, struct file *file);
+
+int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags);
 
-static inline int receive_fd_user(struct file *file, int __user *ufd,
-				  unsigned int o_flags)
-{
-	if (ufd == NULL)
-		return -EFAULT;
-	return __receive_fd(file, ufd, o_flags);
-}
 int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags);
 
 extern void flush_delayed_fput(void);
@@ -109,4 +127,130 @@ extern void __fput_sync(struct file *);
 
 extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
 
+/*
+ * fd_prepare: Combined fd + file allocation cleanup class.
+ * @err: Error code to indicate if allocation succeeded.
+ * @__fd: Allocated fd (may not be accessed directly)
+ * @__file: Allocated struct file pointer (may not be accessed directly)
+ *
+ * Allocates an fd and a file together. On error paths, automatically cleans
+ * up whichever resource was successfully allocated. Allows flexible file
+ * allocation with different functions per usage.
+ *
+ * Do not use directly.
+ */
+struct fd_prepare {
+	s32 err;
+	s32 __fd; /* do not access directly */
+	struct file *__file; /* do not access directly */
+};
+
+/* Typedef for fd_prepare cleanup guards. */
+typedef struct fd_prepare class_fd_prepare_t;
+
+/*
+ * Accessors for fd_prepare class members.
+ * _Generic() is used for zero-cost type safety.
+ */
+#define fd_prepare_fd(_fdf) \
+	(_Generic((_fdf), struct fd_prepare: (_fdf).__fd))
+
+#define fd_prepare_file(_fdf) \
+	(_Generic((_fdf), struct fd_prepare: (_fdf).__file))
+
+/* Do not use directly. */
+static inline void class_fd_prepare_destructor(const struct fd_prepare *fdf)
+{
+	if (unlikely(fdf->err)) {
+		if (likely(fdf->__fd >= 0))
+			put_unused_fd(fdf->__fd);
+		if (unlikely(!IS_ERR_OR_NULL(fdf->__file)))
+			fput(fdf->__file);
+	}
+}
+
+/* Do not use directly. */
+static inline int class_fd_prepare_lock_err(const struct fd_prepare *fdf)
+{
+	if (unlikely(fdf->err))
+		return fdf->err;
+	if (unlikely(fdf->__fd < 0))
+		return fdf->__fd;
+	if (unlikely(IS_ERR(fdf->__file)))
+		return PTR_ERR(fdf->__file);
+	if (unlikely(!fdf->__file))
+		return -ENOMEM;
+	return 0;
+}
+
+/*
+ * __FD_PREPARE_INIT - Helper to initialize fd_prepare class.
+ * @_fd_flags: flags for get_unused_fd_flags()
+ * @_file_owned: expression that returns struct file *
+ *
+ * Returns a struct fd_prepare with fd, file, and err set.
+ * If fd allocation fails, fd will be negative and err will be set. If
+ * fd succeeds but file_init_expr fails, file will be ERR_PTR and err
+ * will be set. The err field is the single source of truth for error
+ * checking.
+ */
+#define __FD_PREPARE_INIT(_fd_flags, _file_owned)                 \
+	({                                                        \
+		struct fd_prepare fdf = {                         \
+			.__fd = get_unused_fd_flags((_fd_flags)), \
+		};                                                \
+		if (likely(fdf.__fd >= 0))                        \
+			fdf.__file = (_file_owned);               \
+		fdf.err = ACQUIRE_ERR(fd_prepare, &fdf);          \
+		fdf;                                              \
+	})
+
+/*
+ * FD_PREPARE - Macro to declare and initialize an fd_prepare variable.
+ *
+ * Declares and initializes an fd_prepare variable with automatic
+ * cleanup. No separate scope required - cleanup happens when variable
+ * goes out of scope.
+ *
+ * @_fdf: name of struct fd_prepare variable to define
+ * @_fd_flags: flags for get_unused_fd_flags()
+ * @_file_owned: struct file to take ownership of (can be expression)
+ */
+#define FD_PREPARE(_fdf, _fd_flags, _file_owned) \
+	CLASS_INIT(fd_prepare, _fdf, __FD_PREPARE_INIT(_fd_flags, _file_owned))
+
+/*
+ * fd_publish - Publish prepared fd and file to the fd table.
+ * @_fdf: struct fd_prepare variable
+ */
+#define fd_publish(_fdf)                                       \
+	({                                                     \
+		struct fd_prepare *fdp = &(_fdf);              \
+		VFS_WARN_ON_ONCE(fdp->err);                    \
+		VFS_WARN_ON_ONCE(fdp->__fd < 0);               \
+		VFS_WARN_ON_ONCE(IS_ERR_OR_NULL(fdp->__file)); \
+		fd_install(fdp->__fd, fdp->__file);            \
+		fdp->__fd;                                     \
+	})
+
+/* Do not use directly. */
+#define __FD_ADD(_fdf, _fd_flags, _file_owned)            \
+	({                                                \
+		FD_PREPARE(_fdf, _fd_flags, _file_owned); \
+		s32 ret = _fdf.err;                       \
+		if (likely(!ret))                         \
+			ret = fd_publish(_fdf);           \
+		ret;                                      \
+	})
+
+/*
+ * FD_ADD - Allocate and install an fd and file in one step.
+ * @_fd_flags: flags for get_unused_fd_flags()
+ * @_file_owned: struct file to take ownership of
+ *
+ * Returns the allocated fd number, or negative error code on failure.
+ */
+#define FD_ADD(_fd_flags, _file_owned) \
+	__FD_ADD(__UNIQUE_ID(fd_prepare), _fd_flags, _file_owned)
+
 #endif /* __LINUX_FILE_H */