Merge tag 'vfs-7.4-rc1.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull file table updates from Christian Brauner:
 "This annotates struct fdtable's fd array with __counted_by_ptr so
  KASAN and the fortified functions can bounds check it against max_fds
  and adds a KUnit suite for fdtable. A follow-up uses __struct_size()
  in the test since sparse doesn't know __builtin_dynamic_object_size().

  FD_PREPARE() is simplified. It was built as an ACQUIRE-style guard on
  infrastructure that was never needed. The ACQUIRE machinery and
  CLASS_INIT() go away, the variable is declared with __cleanup()
  directly, struct fd_prepare loses its err field since the fd either
  holds the descriptor or the error, and callers get a const pointer to
  the guard behind a UNIQUE_ID() name so they can't shadow it. Code
  generation is identical"

* tag 'vfs-7.4-rc1.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  file: make struct fd_prepare const and kill its err field
  cleanup: remove CLASS_INIT()
  file: declare the FD_PREPARE() variable with __cleanup() directly
  file: simplify FD_PREPARE()
  vfs: use __struct_size() in the fdtable KUnit test
  vfs: Add KUnit tests for fdtable
  vfs: Annotate struct fdtable's fd field with __counted_by_ptr

24 files changed, 204 insertions, 157 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 2b54afb31529..5c06f69c9f7f 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -266,9 +266,9 @@ spufs_mkdir(struct inode *dir, struct dentry *dentry, unsigned int flags,
 static int spufs_context_open(const struct path *path)
 {
 	FD_PREPARE(fdf, 0, dentry_open(path, O_RDONLY, current_cred()));
-	if (fdf.err)
-		return fdf.err;
-	fd_prepare_file(fdf)->f_op = &spufs_context_fops;
+	if (fdf->fd < 0)
+		return fdf->fd;
+	fdf->file->f_op = &spufs_context_fops;
 	return fd_publish(fdf);
 }
 
@@ -499,9 +499,9 @@ static int spufs_gang_open(const struct path *path)
 	 * in error path of *_open().
 	 */
 	FD_PREPARE(fdf, 0, dentry_open(path, O_RDONLY, current_cred()));
-	if (fdf.err)
-		return fdf.err;
-	fd_prepare_file(fdf)->f_op = &spufs_gang_fops;
+	if (fdf->fd < 0)
+		return fdf->fd;
+	fdf->file->f_op = &spufs_gang_fops;
 	return fd_publish(fdf);
 }
 
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 5d53bfcdf726..a127e6efd7a1 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -377,11 +377,11 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
 		   anon_inode_getfile("gpio-linehandle", &linehandle_fileops,
 				      lh, O_RDONLY | O_CLOEXEC));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 	retain_and_null_ptr(lh);
 
-	handlereq.fd = fd_prepare_fd(fdf);
+	handlereq.fd = fdf->fd;
 	if (copy_to_user(ip, &handlereq, sizeof(handlereq)))
 		return -EFAULT;
 
@@ -1715,11 +1715,11 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
 	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
 		   anon_inode_getfile("gpio-line", &line_fileops, lr,
 				      O_RDONLY | O_CLOEXEC));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 	retain_and_null_ptr(lr);
 
-	ulr.fd = fd_prepare_fd(fdf);
+	ulr.fd = fdf->fd;
 	if (copy_to_user(ip, &ulr, sizeof(ulr)))
 		return -EFAULT;
 
@@ -2115,11 +2115,11 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
 		   anon_inode_getfile("gpio-event", &lineevent_fileops, le,
 				      O_RDONLY | O_CLOEXEC));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 	retain_and_null_ptr(le);
 
-	eventreq.fd = fd_prepare_fd(fdf);
+	eventreq.fd = fdf->fd;
 	if (copy_to_user(ip, &eventreq, sizeof(eventreq)))
 		return -EFAULT;
 
diff --git a/drivers/gpu/drm/msm/msm_perfcntr.c b/drivers/gpu/drm/msm/msm_perfcntr.c
index ce65b1160955..7fa2e858bd08 100644
--- a/drivers/gpu/drm/msm/msm_perfcntr.c
+++ b/drivers/gpu/drm/msm/msm_perfcntr.c
@@ -543,8 +543,8 @@ msm_ioctl_perfcntr_config(struct drm_device *dev, void *data, struct drm_file *f
 
 		FD_PREPARE(fdf, O_CLOEXEC,
 			   anon_inode_getfile("[msm_perfcntrs]", &stream_fops, stream, 0));
-		if (fdf.err)
-			return fdf.err;
+		if (fdf->fd < 0)
+			return fdf->fd;
 
 		INIT_WORK(&stream->sel_work, sel_worker);
 		kthread_init_work(&stream->sample_work, sample_worker);
diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
index 13e77648807c..e1387f039780 100644
--- a/drivers/media/mc/mc-request.c
+++ b/drivers/media/mc/mc-request.c
@@ -316,15 +316,15 @@ int media_request_alloc(struct media_device *mdev, int *alloc_fd)
 	FD_PREPARE(fdf, O_CLOEXEC,
 		   anon_inode_getfile("request", &request_fops, NULL,
 				      O_CLOEXEC));
-	if (fdf.err) {
-		ret = fdf.err;
+	if (fdf->fd < 0) {
+		ret = fdf->fd;
 		goto err_free_req;
 	}
 
-	fd_prepare_file(fdf)->private_data = req;
+	fdf->file->private_data = req;
 
 	snprintf(req->debug_str, sizeof(req->debug_str), "%u:%d",
-		 atomic_inc_return(&mdev->request_id), fd_prepare_fd(fdf));
+		 atomic_inc_return(&mdev->request_id), fdf->fd);
 	atomic_inc(&mdev->num_requests);
 	dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);
 
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 4a805919bb0c..2857ae37d3c8 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -724,9 +724,9 @@ static int ntsync_obj_get_fd(struct ntsync_obj *obj)
 {
 	FD_PREPARE(fdf, O_CLOEXEC,
 		   anon_inode_getfile("ntsync", &ntsync_obj_fops, obj, O_RDWR));
-	if (fdf.err)
-		return fdf.err;
-	obj->file = fd_prepare_file(fdf);
+	if (fdf->fd < 0)
+		return fdf->fd;
+	obj->file = fdf->file;
 	return fd_publish(fdf);
 }
 
diff --git a/fs/Kconfig b/fs/Kconfig
index 1cb0b3a8b12c..46313f65ee54 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -420,4 +420,12 @@ source "fs/unicode/Kconfig"
 config IO_WQ
 	bool
 
+config FDTABLE_KUNIT_TEST
+	bool "KUnit test for fdtable" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the fdtable KUnit tests, which tests various aspects
+	  of the fdtable structure and allocation.
+
 endmenu
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 9d33a02757d5..52426795752e 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -403,8 +403,8 @@ static int do_eventfd(unsigned int count, int flags)
 	FD_PREPARE(fdf, flags,
 		   anon_inode_getfile_fmode("[eventfd]", &eventfd_fops, ctx,
 					    flags, FMODE_NOWAIT));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	ctx->id = ida_alloc(&eventfd_ida, GFP_KERNEL);
 	retain_and_null_ptr(ctx);
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index e0c4bf88a838..f48b829a710f 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2514,11 +2514,11 @@ static int do_epoll_create(int flags)
 	FD_PREPARE(fdf, O_RDWR | (flags & O_CLOEXEC),
 		   anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
 				      O_RDWR | (flags & O_CLOEXEC)));
-	if (fdf.err) {
+	if (fdf->fd < 0) {
 		ep_clear_and_put(ep);
-		return fdf.err;
+		return fdf->fd;
 	}
-	ep->file = fd_prepare_file(fdf);
+	ep->file = fdf->file;
 	return fd_publish(fdf);
 }
 
diff --git a/fs/file.c b/fs/file.c
index 37f0ba740c39..1166bf130a8d 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1519,17 +1519,17 @@ int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
 		return error;
 
 	FD_PREPARE(fdf, o_flags, file);
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 	get_file(file);
 
 	if (ufd) {
-		error = put_user(fd_prepare_fd(fdf), ufd);
+		error = put_user(fdf->fd, ufd);
 		if (error)
 			return error;
 	}
 
-	__receive_sock(fd_prepare_file(fdf));
+	__receive_sock(fdf->file);
 	return fd_publish(fdf);
 }
 EXPORT_SYMBOL_GPL(receive_fd);
@@ -1657,3 +1657,7 @@ int iterate_fd(struct files_struct *files, unsigned n,
 	return res;
 }
 EXPORT_SYMBOL(iterate_fd);
+
+#ifdef CONFIG_FDTABLE_KUNIT_TEST
+#include "tests/fdtable_kunit.c"
+#endif
diff --git a/fs/namespace.c b/fs/namespace.c
index 59fb227df39f..d3876f0daf2c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4701,16 +4701,16 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 
 	FD_PREPARE(fdf, (flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0,
 		   dentry_open(&new_path, O_PATH, fc->cred));
-	if (fdf.err) {
+	if (fdf->fd < 0) {
 		dissolve_on_fput(no_free_ptr(new_path.mnt));
-		return fdf.err;
+		return fdf->fd;
 	}
 
 	/*
 	 * Attach to an apparent O_PATH fd with a note that we
 	 * need to unmount it, not just simply put it.
 	 */
-	fd_prepare_file(fdf)->f_mode |= FMODE_NEED_UNMOUNT;
+	fdf->file->f_mode |= FMODE_NEED_UNMOUNT;
 	return fd_publish(fdf);
 }
 
@@ -5362,12 +5362,12 @@ SYSCALL_DEFINE5(open_tree_attr, int, dfd, const char __user *, filename,
 		return -EINVAL;
 
 	FD_PREPARE(fdf, flags, vfs_open_tree(dfd, filename, flags));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	if (uattr) {
 		struct mount_kattr kattr = {};
-		struct file *file = fd_prepare_file(fdf);
+		struct file *file = fdf->file;
 		int ret;
 
 		if (flags & OPEN_TREE_CLONE)
diff --git a/fs/nsfs.c b/fs/nsfs.c
index c3b6ae76594a..56ea0bb9ef3a 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -348,8 +348,8 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 			return ret;
 
 		FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
-		if (fdf.err)
-			return fdf.err;
+		if (fdf->fd < 0)
+			return fdf->fd;
 		/*
 		 * If @uinfo is passed return all information about the
 		 * mount namespace as well.
diff --git a/fs/tests/.kunitconfig b/fs/tests/.kunitconfig
new file mode 100644
index 000000000000..de67125a9421
--- /dev/null
+++ b/fs/tests/.kunitconfig
@@ -0,0 +1,2 @@
+CONFIG_KUNIT=y
+CONFIG_FDTABLE_KUNIT_TEST=y
diff --git a/fs/tests/fdtable_kunit.c b/fs/tests/fdtable_kunit.c
new file mode 100644
index 000000000000..c5b028264557
--- /dev/null
+++ b/fs/tests/fdtable_kunit.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+#include <linux/fdtable.h>
+#include <linux/file.h>
+
+static void test_alloc_fdtable(struct kunit *test)
+{
+	struct fdtable *fdt;
+	unsigned int slots = 64;
+
+	fdt = alloc_fdtable(slots);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fdt);
+
+	/* Check that max_fds is set correctly and is >= slots */
+	KUNIT_EXPECT_GE(test, fdt->max_fds, slots);
+
+	/* Check that fd is allocated */
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fdt->fd);
+
+	/*
+	 * Check dynamic object size of fdt->fd if compiler supports
+	 * __counted_by_ptr.
+	 */
+#ifdef CONFIG_CC_HAS_COUNTED_BY_PTR
+	KUNIT_EXPECT_EQ(test, __struct_size(fdt->fd),
+			fdt->max_fds * sizeof(struct file *));
+#endif
+
+	__free_fdtable(fdt);
+}
+
+static void test_dup_fd(struct kunit *test)
+{
+	struct files_struct *newf;
+	struct fdtable *fdt;
+
+	newf = dup_fd(&init_files, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, newf);
+
+	fdt = rcu_dereference_raw(newf->fdt);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fdt);
+
+	/* Check that max_fds is set correctly and is >= NR_OPEN_DEFAULT */
+	KUNIT_EXPECT_GE(test, fdt->max_fds, NR_OPEN_DEFAULT);
+
+	/* Check that fd is allocated */
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fdt->fd);
+
+	/*
+	 * Check dynamic object size of fdt->fd if compiler supports
+	 * __counted_by_ptr.
+	 */
+#ifdef CONFIG_CC_HAS_COUNTED_BY_PTR
+	KUNIT_EXPECT_EQ(test, __struct_size(fdt->fd),
+			fdt->max_fds * sizeof(struct file *));
+#endif
+
+	put_files_struct(newf);
+}
+
+static struct kunit_case fdtable_test_cases[] = {
+	KUNIT_CASE(test_alloc_fdtable),
+	KUNIT_CASE(test_dup_fd),
+	{}
+};
+
+static struct kunit_suite fdtable_test_suite = {
+	.name = "fdtable",
+	.test_cases = fdtable_test_cases,
+};
+
+kunit_test_suite(fdtable_test_suite);
diff --git a/fs/xfs/xfs_handle.c b/fs/xfs/xfs_handle.c
index 0689cade8f74..303bcff64459 100644
--- a/fs/xfs/xfs_handle.c
+++ b/fs/xfs/xfs_handle.c
@@ -272,11 +272,11 @@ xfs_open_by_handle(
 	path.mnt = mntget(parfilp->f_path.mnt);
 
 	FD_PREPARE(fdf, 0, dentry_open(&path, hreq->oflags, cred));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	if (S_ISREG(inode->i_mode)) {
-		struct file *filp = fd_prepare_file(fdf);
+		struct file *filp = fdf->file;
 
 		filp->f_flags |= O_NOATIME;
 		filp->f_mode |= FMODE_NOCMTIME;
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index b1b5698cbf1b..1fb8058b897d 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -261,10 +261,6 @@ const volatile void * __must_check_fn(const volatile void *val)
  * CLASS(name, var)(args...):
  *	declare the variable @var as an instance of the named class
  *
- * CLASS_INIT(name, var, init_expr):
- *	declare the variable @var as an instance of the named class with
- *	custom initialization expression.
- *
  * Ex.
  *
  * DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd)
@@ -302,9 +298,6 @@ static __always_inline class_##_name##_t class_##_name##ext##_constructor(_init_
 	class_##_name##_t var __cleanup(class_##_name##_destructor) =	\
 		class_##_name##_constructor
 
-#define CLASS_INIT(_name, _var, _init_expr)                             \
-        class_##_name##_t _var __cleanup(class_##_name##_destructor) = (_init_expr)
-
 #define __scoped_class(_name, var, _label, args...)        \
 	for (CLASS(_name, var)(args); ; ({ goto _label; })) \
 		if (0) {                                   \
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index afdfaad381df..c0cabd9c79ec 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -25,7 +25,7 @@
 
 struct fdtable {
 	unsigned int max_fds;
-	struct file __rcu **fd;      /* current fd array */
+	struct file __rcu **fd __counted_by_ptr(max_fds);      /* current fd array */
 	unsigned long *close_on_exec;
 	unsigned long *open_fds;
 	unsigned long *full_fds_bits;
diff --git a/include/linux/file.h b/include/linux/file.h
index 27484b444d31..41c3c0be1064 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -12,6 +12,7 @@
 #include <linux/errno.h>
 #include <linux/cleanup.h>
 #include <linux/err.h>
+#include <linux/vfsdebug.h>
 
 struct file;
 
@@ -129,117 +130,84 @@ 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)
+ * @fd: Allocated fd
+ * @file: Allocated struct file pointer
  *
  * 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.
+ * Do not declare directly, use FD_PREPARE().
  */
 struct fd_prepare {
-	s32 err;
-	s32 __fd; /* do not access directly */
-	struct file *__file; /* do not access directly */
+	int fd;
+	struct file *file;
 };
 
-/* 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)
+static __always_inline void __fd_prepare_cleanup(const struct fd_prepare *fdf)
 {
-	if (unlikely(fdf->__fd >= 0))
-		put_unused_fd(fdf->__fd);
-	if (unlikely(!IS_ERR_OR_NULL(fdf->__file)))
-		fput(fdf->__file);
+	if (unlikely(fdf->fd >= 0)) {
+		put_unused_fd(fdf->fd);
+		fput(fdf->file);
+	}
 }
 
 /* Do not use directly. */
-static inline int class_fd_prepare_lock_err(const struct fd_prepare *fdf)
+static __always_inline struct fd_prepare __fd_prepare(int fd, struct file *file)
 {
-	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;
+	if (fd >= 0 && IS_ERR_OR_NULL(file)) {
+		int err = file ? PTR_ERR(file) : -ENOMEM;
+
+		put_unused_fd(fd);
+		fd = err;
+		file = NULL;
+	}
+	return (struct fd_prepare){ .fd = fd, .file = file };
 }
 
 /*
- * __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.
+ * FD_PREPARE - Declare and initialize an fd_prepare instance.
  *
- * Declares and initializes an fd_prepare variable with automatic
- * cleanup. No separate scope required - cleanup happens when variable
- * goes out of scope.
+ * This allocates a new fd and only evaluates @_file_owned if the
+ * allocation succeeded. Cleanup happens when the variable goes out of
+ * scope and the guard releases whichever of the descriptor and the file
+ * was allocated. If fd_publish() was called the fd and file are
+ * published and cleanup becomes a nop.
  *
- * @_fdf: name of struct fd_prepare variable to define
+ * @_fdf: name of the const struct fd_prepare pointer to define
  * @_fd_flags: flags for get_unused_fd_flags()
  * @_file_owned: struct file to take ownership of (can be expression)
  */
+#define __FD_PREPARE(_guard, _fdf, _fd_flags, _file_owned)		\
+	struct fd_prepare _guard __cleanup(__fd_prepare_cleanup) = ({	\
+		int __fd = get_unused_fd_flags(_fd_flags);		\
+		__fd_prepare(__fd, __fd < 0 ? NULL : (_file_owned));	\
+	});								\
+	const struct fd_prepare *const _fdf = &_guard
+
 #define FD_PREPARE(_fdf, _fd_flags, _file_owned) \
-	CLASS_INIT(fd_prepare, _fdf, __FD_PREPARE_INIT(_fd_flags, _file_owned))
+	__FD_PREPARE(__UNIQUE_ID(fd_prepare), _fdf, _fd_flags, _file_owned)
 
 /*
  * fd_publish - Publish prepared fd and file to the fd table.
- * @_fdf: struct fd_prepare variable
+ * @fdf: struct fd_prepare pointer defined by FD_PREPARE()
  */
-#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);            \
-		retain_and_null_ptr(fdp->__file);              \
-		take_fd(fdp->__fd);                            \
-	})
+static __always_inline int fd_publish(const struct fd_prepare *fdf)
+{
+	/* Callers only get a const view, the guard itself is writable. */
+	struct fd_prepare *guard = (struct fd_prepare *)fdf;
+
+	VFS_WARN_ON_ONCE(guard->fd < 0);
+	fd_install(guard->fd, guard->file);
+	return take_fd(guard->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;                                      \
+#define __FD_ADD(_fdf, _fd_flags, _file_owned)			\
+	({							\
+		FD_PREPARE(_fdf, _fd_flags, _file_owned);	\
+		_fdf->fd < 0 ? _fdf->fd : fd_publish(_fdf);	\
 	})
 
 /*
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index b318ed697998..9f0b4d850c12 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -257,17 +257,17 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	FD_PREPARE(fdf, O_RDWR | O_CLOEXEC,
 		   anon_inode_create_getfile("[io_uring_mock]", fops, mf,
 					     O_RDWR | O_CLOEXEC, NULL));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	retain_and_null_ptr(mf);
-	file = fd_prepare_file(fdf);
+	file = fdf->file;
 	file->f_mode |= FMODE_READ | FMODE_CAN_READ | FMODE_WRITE |
 			FMODE_CAN_WRITE | FMODE_LSEEK;
 	if (mc.flags & IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
 		file->f_mode |= FMODE_NOWAIT;
 
-	mc.out_fd = fd_prepare_fd(fdf);
+	mc.out_fd = fdf->fd;
 	if (copy_to_user(uarg, &mc, uarg_size))
 		return -EFAULT;
 
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index b40eb404adab..d9191df5de22 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -643,11 +643,11 @@ int bpf_iter_new_fd(struct bpf_link *link)
 	flags = O_RDONLY | O_CLOEXEC;
 
 	FD_PREPARE(fdf, flags, anon_inode_getfile("bpf_iter", &bpf_iter_fops, NULL, flags));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	iter_link = container_of(link, struct bpf_iter_link, link);
-	err = prepare_seq_file(fd_prepare_file(fdf), iter_link);
+	err = prepare_seq_file(fdf->file, iter_link);
 	if (err)
 		return err; /* Automatic cleanup handles fput */
 
diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
index e85a179523f0..da915a4f972b 100644
--- a/kernel/bpf/token.c
+++ b/kernel/bpf/token.c
@@ -169,8 +169,8 @@ int bpf_token_create(union bpf_attr *attr)
 	FD_PREPARE(fdf, O_CLOEXEC,
 		   alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME,
 				     O_RDWR, &bpf_token_fops));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	token = kzalloc_obj(*token, GFP_USER);
 	if (!token)
@@ -190,7 +190,7 @@ int bpf_token_create(union bpf_attr *attr)
 		return err;
 
 	get_user_ns(token->userns);
-	fd_prepare_file(fdf)->private_data = no_free_ptr(token);
+	fdf->file->private_data = no_free_ptr(token);
 	return fd_publish(fdf);
 }
 
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 74f04c323c50..6a033df14027 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -4811,12 +4811,12 @@ static int new_userfaultfd(int flags)
 		   anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
 					     O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS),
 					     NULL));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
 	/* prevent the mm struct to be freed */
 	mmgrab(ctx->mm);
-	fd_prepare_file(fdf)->f_mode |= FMODE_NOWAIT;
+	fdf->file->f_mode |= FMODE_NOWAIT;
 	retain_and_null_ptr(ctx);
 	return fd_publish(fdf);
 }
diff --git a/net/core/scm.c b/net/core/scm.c
index f0d44ecdb11f..15c330784a69 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -364,14 +364,14 @@ int scm_recv_one_fd(struct file *f, int __user *ufd, unsigned int flags,
 		return notrunc ? put_user(error, ufd) : error;
 
 	FD_PREPARE(fdf, flags, get_file(f));
-	if (fdf.err)
-		return fdf.err;
+	if (fdf->fd < 0)
+		return fdf->fd;
 
-	error = put_user(fd_prepare_fd(fdf), ufd);
+	error = put_user(fdf->fd, ufd);
 	if (error)
 		return error;
 
-	__receive_sock(fd_prepare_file(fdf));
+	__receive_sock(fdf->file);
 	return fd_publish(fdf);
 }
 
diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c
index 3fd4fef9bab1..73b8314d9010 100644
--- a/net/handshake/netlink.c
+++ b/net/handshake/netlink.c
@@ -107,17 +107,17 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
 	req = handshake_req_next(hn, class);
 	if (req) {
 		FD_PREPARE(fdf, O_CLOEXEC, req->hr_file);
-		if (fdf.err) {
+		if (fdf->fd < 0) {
 			fput(req->hr_file); /* drop ref from handshake_req_next() */
-			err = fdf.err;
+			err = fdf->fd;
 			goto out_complete;
 		}
 
-		err = req->hr_proto->hp_accept(req, info, fd_prepare_fd(fdf));
+		err = req->hr_proto->hp_accept(req, info, fdf->fd);
 		if (err)
 			goto out_complete; /* Automatic cleanup handles fput */
 
-		trace_handshake_cmd_accept(net, req, req->hr_sk, fd_prepare_fd(fdf));
+		trace_handshake_cmd_accept(net, req, req->hr_sk, fdf->fd);
 		fd_publish(fdf);
 		return 0;
 	}
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 71af69d442f2..962ee2c4acd2 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1580,10 +1580,10 @@ static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 		struct kcm_clone info;
 
 		FD_PREPARE(fdf, 0, kcm_clone(sock));
-		if (fdf.err)
-			return fdf.err;
+		if (fdf->fd < 0)
+			return fdf->fd;
 
-		info.fd = fd_prepare_fd(fdf);
+		info.fd = fdf->fd;
 		if (copy_to_user((void __user *)arg, &info, sizeof(info)))
 			return -EFAULT;