Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1634 insertions, 0 deletions

diff --git a/fs/open.c b/fs/open.c
new file mode 100644
index 000000000..6b1c14e68
--- /dev/null
+++ b/fs/open.c
@@ -0,0 +1,1634 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/open.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/fsnotify.h>
+#include <linux/module.h>
+#include <linux/tty.h>
+#include <linux/namei.h>
+#include <linux/backing-dev.h>
+#include <linux/capability.h>
+#include <linux/securebits.h>
+#include <linux/security.h>
+#include <linux/mount.h>
+#include <linux/fcntl.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+#include <linux/personality.h>
+#include <linux/pagemap.h>
+#include <linux/syscalls.h>
+#include <linux/rcupdate.h>
+#include <linux/audit.h>
+#include <linux/falloc.h>
+#include <linux/fs_struct.h>
+#include <linux/dnotify.h>
+#include <linux/compat.h>
+#include <linux/mnt_idmapping.h>
+#include <linux/filelock.h>
+
+#include "internal.h"
+
+int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry,
+		loff_t length, unsigned int time_attrs, struct file *filp)
+{
+	int ret;
+	struct iattr newattrs;
+
+	/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
+	if (length < 0)
+		return -EINVAL;
+
+	newattrs.ia_size = length;
+	newattrs.ia_valid = ATTR_SIZE | time_attrs;
+	if (filp) {
+		newattrs.ia_file = filp;
+		newattrs.ia_valid |= ATTR_FILE;
+	}
+
+	/* Remove suid, sgid, and file capabilities on truncate too */
+	ret = dentry_needs_remove_privs(idmap, dentry);
+	if (ret < 0)
+		return ret;
+	if (ret)
+		newattrs.ia_valid |= ret | ATTR_FORCE;
+
+	ret = inode_lock_killable(dentry->d_inode);
+	if (ret)
+		return ret;
+
+	/* Note any delegations or leases have already been broken: */
+	ret = notify_change(idmap, dentry, &newattrs, NULL);
+	inode_unlock(dentry->d_inode);
+	return ret;
+}
+
+int vfs_truncate(const struct path *path, loff_t length)
+{
+	struct mnt_idmap *idmap;
+	struct inode *inode;
+	int error;
+
+	inode = path->dentry->d_inode;
+
+	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
+	if (S_ISDIR(inode->i_mode))
+		return -EISDIR;
+	if (!S_ISREG(inode->i_mode))
+		return -EINVAL;
+
+	idmap = mnt_idmap(path->mnt);
+	error = inode_permission(idmap, inode, MAY_WRITE);
+	if (error)
+		return error;
+
+	error = fsnotify_truncate_perm(path, length);
+	if (error)
+		return error;
+
+	error = mnt_want_write(path->mnt);
+	if (error)
+		return error;
+
+	error = -EPERM;
+	if (IS_APPEND(inode))
+		goto mnt_drop_write_and_out;
+
+	error = get_write_access(inode);
+	if (error)
+		goto mnt_drop_write_and_out;
+
+	/*
+	 * Make sure that there are no leases.  get_write_access() protects
+	 * against the truncate racing with a lease-granting setlease().
+	 */
+	error = break_lease(inode, O_WRONLY);
+	if (error)
+		goto put_write_and_out;
+
+	error = security_path_truncate(path);
+	if (!error)
+		error = do_truncate(idmap, path->dentry, length, 0, NULL);
+
+put_write_and_out:
+	put_write_access(inode);
+mnt_drop_write_and_out:
+	mnt_drop_write(path->mnt);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(vfs_truncate);
+
+int ksys_truncate(const char __user *pathname, loff_t length)
+{
+	unsigned int lookup_flags = LOOKUP_FOLLOW;
+	struct path path;
+	int error;
+
+	if (length < 0)	/* sorry, but loff_t says... */
+		return -EINVAL;
+
+	CLASS(filename, name)(pathname);
+retry:
+	error = filename_lookup(AT_FDCWD, name, lookup_flags, &path, NULL);
+	if (!error) {
+		error = vfs_truncate(&path, length);
+		path_put(&path);
+		if (retry_estale(error, lookup_flags)) {
+			lookup_flags |= LOOKUP_REVAL;
+			goto retry;
+		}
+	}
+	return error;
+}
+
+SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
+{
+	return ksys_truncate(path, length);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
+{
+	return ksys_truncate(path, length);
+}
+#endif
+
+int do_ftruncate(struct file *file, loff_t length, unsigned int flags)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
+		return -EINVAL;
+
+	/*
+	 * Cannot ftruncate over 2^31 bytes without large file support, either
+	 * through opening with O_LARGEFILE or by using ftruncate64().
+	 */
+	if (length > MAX_NON_LFS &&
+	    !(file->f_flags & O_LARGEFILE) && !(flags & FTRUNCATE_LFS))
+		return -EINVAL;
+
+	/* Check IS_APPEND on real upper inode */
+	if (IS_APPEND(file_inode(file)))
+		return -EPERM;
+
+	error = security_file_truncate(file);
+	if (error)
+		return error;
+
+	error = fsnotify_truncate_perm(&file->f_path, length);
+	if (error)
+		return error;
+
+	scoped_guard(super_write, inode->i_sb)
+		return do_truncate(file_mnt_idmap(file), dentry, length,
+				   ATTR_MTIME | ATTR_CTIME, file);
+}
+
+int ksys_ftruncate(unsigned int fd, loff_t length, unsigned int flags)
+{
+	if (length < 0)
+		return -EINVAL;
+	CLASS(fd, f)(fd);
+	if (fd_empty(f))
+		return -EBADF;
+
+	return do_ftruncate(fd_file(f), length, flags);
+}
+
+SYSCALL_DEFINE2(ftruncate, unsigned int, fd, off_t, length)
+{
+	return ksys_ftruncate(fd, length, 0);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_off_t, length)
+{
+	return ksys_ftruncate(fd, length, 0);
+}
+#endif
+
+/* LFS versions of truncate are only needed on 32 bit machines */
+#if BITS_PER_LONG == 32
+SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
+{
+	return ksys_truncate(path, length);
+}
+
+SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
+{
+	return ksys_ftruncate(fd, length, FTRUNCATE_LFS);
+}
+#endif /* BITS_PER_LONG == 32 */
+
+#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_TRUNCATE64)
+COMPAT_SYSCALL_DEFINE3(truncate64, const char __user *, pathname,
+		       compat_arg_u64_dual(length))
+{
+	return ksys_truncate(pathname, compat_arg_u64_glue(length));
+}
+#endif
+
+#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FTRUNCATE64)
+COMPAT_SYSCALL_DEFINE3(ftruncate64, unsigned int, fd,
+		       compat_arg_u64_dual(length))
+{
+	return ksys_ftruncate(fd, compat_arg_u64_glue(length), FTRUNCATE_LFS);
+}
+#endif
+
+int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+	int ret;
+	loff_t sum;
+
+	if (offset < 0 || len <= 0)
+		return -EINVAL;
+
+	if (mode & ~(FALLOC_FL_MODE_MASK | FALLOC_FL_KEEP_SIZE))
+		return -EOPNOTSUPP;
+
+	/*
+	 * Modes are exclusive, even if that is not obvious from the encoding
+	 * as bit masks and the mix with the flag in the same namespace.
+	 *
+	 * To make things even more complicated, FALLOC_FL_ALLOCATE_RANGE is
+	 * encoded as no bit set.
+	 */
+	switch (mode & FALLOC_FL_MODE_MASK) {
+	case FALLOC_FL_ALLOCATE_RANGE:
+	case FALLOC_FL_UNSHARE_RANGE:
+	case FALLOC_FL_ZERO_RANGE:
+		break;
+	case FALLOC_FL_PUNCH_HOLE:
+		if (!(mode & FALLOC_FL_KEEP_SIZE))
+			return -EOPNOTSUPP;
+		break;
+	case FALLOC_FL_COLLAPSE_RANGE:
+	case FALLOC_FL_INSERT_RANGE:
+	case FALLOC_FL_WRITE_ZEROES:
+		if (mode & FALLOC_FL_KEEP_SIZE)
+			return -EOPNOTSUPP;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+
+	/*
+	 * On append-only files only space preallocation is supported.
+	 */
+	if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
+		return -EPERM;
+
+	if (IS_IMMUTABLE(inode))
+		return -EPERM;
+
+	/*
+	 * We cannot allow any fallocate operation on an active swapfile
+	 */
+	if (IS_SWAPFILE(inode))
+		return -ETXTBSY;
+
+	/*
+	 * Revalidate the write permissions, in case security policy has
+	 * changed since the files were opened.
+	 */
+	ret = security_file_permission(file, MAY_WRITE);
+	if (ret)
+		return ret;
+
+	ret = fsnotify_file_area_perm(file, MAY_WRITE, &offset, len);
+	if (ret)
+		return ret;
+
+	if (S_ISFIFO(inode->i_mode))
+		return -ESPIPE;
+
+	if (S_ISDIR(inode->i_mode))
+		return -EISDIR;
+
+	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+		return -ENODEV;
+
+	/* Check for wraparound */
+	if (check_add_overflow(offset, len, &sum))
+		return -EFBIG;
+
+	if (sum > inode->i_sb->s_maxbytes)
+		return -EFBIG;
+
+	if (!file->f_op->fallocate)
+		return -EOPNOTSUPP;
+
+	file_start_write(file);
+	ret = file->f_op->fallocate(file, mode, offset, len);
+
+	/*
+	 * Create inotify and fanotify events.
+	 *
+	 * To keep the logic simple always create events if fallocate succeeds.
+	 * This implies that events are even created if the file size remains
+	 * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
+	 */
+	if (ret == 0)
+		fsnotify_modify(file);
+
+	file_end_write(file);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vfs_fallocate);
+
+int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
+{
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f))
+		return -EBADF;
+
+	return vfs_fallocate(fd_file(f), mode, offset, len);
+}
+
+SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
+{
+	return ksys_fallocate(fd, mode, offset, len);
+}
+
+#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FALLOCATE)
+COMPAT_SYSCALL_DEFINE6(fallocate, int, fd, int, mode, compat_arg_u64_dual(offset),
+		       compat_arg_u64_dual(len))
+{
+	return ksys_fallocate(fd, mode, compat_arg_u64_glue(offset),
+			      compat_arg_u64_glue(len));
+}
+#endif
+
+/*
+ * access() needs to use the real uid/gid, not the effective uid/gid.
+ * We do this by temporarily clearing all FS-related capabilities and
+ * switching the fsuid/fsgid around to the real ones.
+ *
+ * Creating new credentials is expensive, so we try to skip doing it,
+ * which we can if the result would match what we already got.
+ */
+static bool access_need_override_creds(int flags)
+{
+	const struct cred *cred;
+
+	if (flags & AT_EACCESS)
+		return false;
+
+	cred = current_cred();
+	if (!uid_eq(cred->fsuid, cred->uid) ||
+	    !gid_eq(cred->fsgid, cred->gid))
+		return true;
+
+	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
+		kuid_t root_uid = make_kuid(cred->user_ns, 0);
+		if (!uid_eq(cred->uid, root_uid)) {
+			if (!cap_isclear(cred->cap_effective))
+				return true;
+		} else {
+			if (!cap_isidentical(cred->cap_effective,
+			    cred->cap_permitted))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+static const struct cred *access_override_creds(void)
+{
+	struct cred *override_cred;
+
+	override_cred = prepare_creds();
+	if (!override_cred)
+		return NULL;
+
+	/*
+	 * XXX access_need_override_creds performs checks in hopes of skipping
+	 * this work. Make sure it stays in sync if making any changes in this
+	 * routine.
+	 */
+
+	override_cred->fsuid = override_cred->uid;
+	override_cred->fsgid = override_cred->gid;
+
+	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
+		/* Clear the capabilities if we switch to a non-root user */
+		kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
+		if (!uid_eq(override_cred->uid, root_uid))
+			cap_clear(override_cred->cap_effective);
+		else
+			override_cred->cap_effective =
+				override_cred->cap_permitted;
+	}
+
+	/*
+	 * The new set of credentials can *only* be used in
+	 * task-synchronous circumstances, and does not need
+	 * RCU freeing, unless somebody then takes a separate
+	 * reference to it.
+	 *
+	 * NOTE! This is _only_ true because this credential
+	 * is used purely for override_creds() that installs
+	 * it as the subjective cred. Other threads will be
+	 * accessing ->real_cred, not the subjective cred.
+	 *
+	 * If somebody _does_ make a copy of this (using the
+	 * 'get_current_cred()' function), that will clear the
+	 * non_rcu field, because now that other user may be
+	 * expecting RCU freeing. But normal thread-synchronous
+	 * cred accesses will keep things non-racy to avoid RCU
+	 * freeing.
+	 */
+	override_cred->non_rcu = 1;
+	return override_creds(override_cred);
+}
+
+static int do_faccessat(int dfd, const char __user *filename, int mode, int flags)
+{
+	struct path path;
+	struct inode *inode;
+	int res;
+	unsigned int lookup_flags = LOOKUP_FOLLOW;
+	const struct cred *old_cred = NULL;
+
+	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
+		return -EINVAL;
+
+	if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
+		return -EINVAL;
+
+	if (flags & AT_SYMLINK_NOFOLLOW)
+		lookup_flags &= ~LOOKUP_FOLLOW;
+
+	if (access_need_override_creds(flags)) {
+		old_cred = access_override_creds();
+		if (!old_cred)
+			return -ENOMEM;
+	}
+
+	CLASS(filename_uflags, name)(filename, flags);
+retry:
+	res = filename_lookup(dfd, name, lookup_flags, &path, NULL);
+	if (res)
+		goto out;
+
+	inode = d_backing_inode(path.dentry);
+
+	if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
+		/*
+		 * MAY_EXEC on regular files is denied if the fs is mounted
+		 * with the "noexec" flag.
+		 */
+		res = -EACCES;
+		if (path_noexec(&path))
+			goto out_path_release;
+	}
+
+	res = inode_permission(mnt_idmap(path.mnt), inode, mode | MAY_ACCESS);
+	/* SuS v2 requires we report a read only fs too */
+	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
+		goto out_path_release;
+	/*
+	 * This is a rare case where using __mnt_is_readonly()
+	 * is OK without a mnt_want/drop_write() pair.  Since
+	 * no actual write to the fs is performed here, we do
+	 * not need to telegraph to that to anyone.
+	 *
+	 * By doing this, we accept that this access is
+	 * inherently racy and know that the fs may change
+	 * state before we even see this result.
+	 */
+	if (__mnt_is_readonly(path.mnt))
+		res = -EROFS;
+
+out_path_release:
+	path_put(&path);
+	if (retry_estale(res, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
+out:
+	if (old_cred)
+		put_cred(revert_creds(old_cred));
+
+	return res;
+}
+
+SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
+{
+	return do_faccessat(dfd, filename, mode, 0);
+}
+
+SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
+		int, flags)
+{
+	return do_faccessat(dfd, filename, mode, flags);
+}
+
+SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
+{
+	return do_faccessat(AT_FDCWD, filename, mode, 0);
+}
+
+SYSCALL_DEFINE1(chdir, const char __user *, filename)
+{
+	struct path path;
+	int error;
+	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+	CLASS(filename, name)(filename);
+retry:
+	error = filename_lookup(AT_FDCWD, name, lookup_flags, &path, NULL);
+	if (!error) {
+		error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
+		if (!error)
+			set_fs_pwd(current->fs, &path);
+		path_put(&path);
+		if (retry_estale(error, lookup_flags)) {
+			lookup_flags |= LOOKUP_REVAL;
+			goto retry;
+		}
+	}
+	return error;
+}
+
+SYSCALL_DEFINE1(fchdir, unsigned int, fd)
+{
+	int error;
+
+	if ((int)fd == FD_FAILFS_ROOT)
+		return failfs_current_chdir();
+
+	CLASS(fd_raw, f)(fd);
+	if (fd_empty(f))
+		return -EBADF;
+
+	if (!d_can_lookup(fd_file(f)->f_path.dentry))
+		return -ENOTDIR;
+
+	error = file_permission(fd_file(f), MAY_EXEC | MAY_CHDIR);
+	if (!error)
+		set_fs_pwd(current->fs, &fd_file(f)->f_path);
+	return error;
+}
+
+SYSCALL_DEFINE1(chroot, const char __user *, filename)
+{
+	struct path path;
+	int error;
+	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+	CLASS(filename, name)(filename);
+retry:
+	error = filename_lookup(AT_FDCWD, name, lookup_flags, &path, NULL);
+	if (error)
+		return error;
+
+	error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
+	if (error)
+		goto dput_and_out;
+
+	error = -EPERM;
+	if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
+		goto dput_and_out;
+	error = security_path_chroot(&path);
+	if (!error)
+		set_fs_root(current->fs, &path);
+dput_and_out:
+	path_put(&path);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
+	return error;
+}
+
+SYSCALL_DEFINE2(fchroot, int, fd, unsigned int, flags)
+{
+	struct path path;
+	int error;
+
+	if (flags)
+		return -EINVAL;
+
+	if (fd == FD_FAILFS_ROOT) {
+		if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT)) {
+			if (!task_no_new_privs(current))
+				return -EPERM;
+			/* A shared fs_struct lets a sibling exec setuid past the check above. */
+			if (current->fs->users != 1)
+				return -EINVAL;
+			/* Moving the root to failfs lifts the old root's ".." barrier. */
+			if (current_chrooted())
+				return -EPERM;
+		}
+		failfs_get_root(&path);
+	} else {
+		CLASS(fd_raw, f)(fd);
+		if (fd_empty(f))
+			return -EBADF;
+
+		if (!d_can_lookup(fd_file(f)->f_path.dentry))
+			return -ENOTDIR;
+
+		error = file_permission(fd_file(f), MAY_EXEC | MAY_CHDIR);
+		if (error)
+			return error;
+
+		if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
+			return -EPERM;
+
+		path = fd_file(f)->f_path;
+		path_get(&path);
+	}
+
+	error = security_path_chroot(&path);
+	if (!error)
+		set_fs_root(current->fs, &path);
+	path_put(&path);
+	return error;
+}
+
+int chmod_common(const struct path *path, umode_t mode)
+{
+	struct inode *inode = path->dentry->d_inode;
+	struct delegated_inode delegated_inode = { };
+	struct iattr newattrs;
+	int error;
+
+	error = mnt_want_write(path->mnt);
+	if (error)
+		return error;
+retry_deleg:
+	error = inode_lock_killable(inode);
+	if (error)
+		goto out_mnt_unlock;
+	error = security_path_chmod(path, mode);
+	if (error)
+		goto out_unlock;
+	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
+	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+	error = notify_change(mnt_idmap(path->mnt), path->dentry,
+			      &newattrs, &delegated_inode);
+out_unlock:
+	inode_unlock(inode);
+	if (is_delegated(&delegated_inode)) {
+		error = break_deleg_wait(&delegated_inode);
+		if (!error)
+			goto retry_deleg;
+	}
+out_mnt_unlock:
+	mnt_drop_write(path->mnt);
+	return error;
+}
+
+int vfs_fchmod(struct file *file, umode_t mode)
+{
+	audit_file(file);
+	return chmod_common(&file->f_path, mode);
+}
+
+SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
+{
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f))
+		return -EBADF;
+
+	return vfs_fchmod(fd_file(f), mode);
+}
+
+static int do_fchmodat(int dfd, const char __user *filename, umode_t mode,
+		       unsigned int flags)
+{
+	struct path path;
+	int error;
+	unsigned int lookup_flags;
+
+	if (unlikely(flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)))
+		return -EINVAL;
+
+	lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
+	CLASS(filename_uflags, name)(filename, flags);
+retry:
+	error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
+	if (!error) {
+		error = chmod_common(&path, mode);
+		path_put(&path);
+		if (retry_estale(error, lookup_flags)) {
+			lookup_flags |= LOOKUP_REVAL;
+			goto retry;
+		}
+	}
+	return error;
+}
+
+SYSCALL_DEFINE4(fchmodat2, int, dfd, const char __user *, filename,
+		umode_t, mode, unsigned int, flags)
+{
+	return do_fchmodat(dfd, filename, mode, flags);
+}
+
+SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
+		umode_t, mode)
+{
+	return do_fchmodat(dfd, filename, mode, 0);
+}
+
+SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
+{
+	return do_fchmodat(AT_FDCWD, filename, mode, 0);
+}
+
+/*
+ * Check whether @kuid is valid and if so generate and set vfsuid_t in
+ * ia_vfsuid.
+ *
+ * Return: true if @kuid is valid, false if not.
+ */
+static inline bool setattr_vfsuid(struct iattr *attr, kuid_t kuid)
+{
+	if (!uid_valid(kuid))
+		return false;
+	attr->ia_valid |= ATTR_UID;
+	attr->ia_vfsuid = VFSUIDT_INIT(kuid);
+	return true;
+}
+
+/*
+ * Check whether @kgid is valid and if so generate and set vfsgid_t in
+ * ia_vfsgid.
+ *
+ * Return: true if @kgid is valid, false if not.
+ */
+static inline bool setattr_vfsgid(struct iattr *attr, kgid_t kgid)
+{
+	if (!gid_valid(kgid))
+		return false;
+	attr->ia_valid |= ATTR_GID;
+	attr->ia_vfsgid = VFSGIDT_INIT(kgid);
+	return true;
+}
+
+int chown_common(const struct path *path, uid_t user, gid_t group)
+{
+	struct mnt_idmap *idmap;
+	struct user_namespace *fs_userns;
+	struct inode *inode = path->dentry->d_inode;
+	struct delegated_inode delegated_inode = { };
+	int error;
+	struct iattr newattrs;
+	kuid_t uid;
+	kgid_t gid;
+
+	uid = make_kuid(current_user_ns(), user);
+	gid = make_kgid(current_user_ns(), group);
+
+	idmap = mnt_idmap(path->mnt);
+	fs_userns = i_user_ns(inode);
+
+retry_deleg:
+	newattrs.ia_vfsuid = INVALID_VFSUID;
+	newattrs.ia_vfsgid = INVALID_VFSGID;
+	newattrs.ia_valid =  ATTR_CTIME;
+	if ((user != (uid_t)-1) && !setattr_vfsuid(&newattrs, uid))
+		return -EINVAL;
+	if ((group != (gid_t)-1) && !setattr_vfsgid(&newattrs, gid))
+		return -EINVAL;
+	error = inode_lock_killable(inode);
+	if (error)
+		return error;
+	if (!S_ISDIR(inode->i_mode))
+		newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV |
+				     setattr_should_drop_sgid(idmap, inode);
+	/* Continue to send actual fs values, not the mount values. */
+	error = security_path_chown(
+		path,
+		from_vfsuid(idmap, fs_userns, newattrs.ia_vfsuid),
+		from_vfsgid(idmap, fs_userns, newattrs.ia_vfsgid));
+	if (!error)
+		error = notify_change(idmap, path->dentry, &newattrs,
+				      &delegated_inode);
+	inode_unlock(inode);
+	if (is_delegated(&delegated_inode)) {
+		error = break_deleg_wait(&delegated_inode);
+		if (!error)
+			goto retry_deleg;
+	}
+	return error;
+}
+
+int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
+		int flag)
+{
+	struct path path;
+	int error;
+	int lookup_flags;
+
+	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
+		return -EINVAL;
+
+	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
+	CLASS(filename_uflags, name)(filename, flag);
+retry:
+	error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
+	if (!error) {
+		error = mnt_want_write(path.mnt);
+		if (!error) {
+			error = chown_common(&path, user, group);
+			mnt_drop_write(path.mnt);
+		}
+		path_put(&path);
+		if (retry_estale(error, lookup_flags)) {
+			lookup_flags |= LOOKUP_REVAL;
+			goto retry;
+		}
+	}
+	return error;
+}
+
+SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
+		gid_t, group, int, flag)
+{
+	return do_fchownat(dfd, filename, user, group, flag);
+}
+
+SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
+{
+	return do_fchownat(AT_FDCWD, filename, user, group, 0);
+}
+
+SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
+{
+	return do_fchownat(AT_FDCWD, filename, user, group,
+			   AT_SYMLINK_NOFOLLOW);
+}
+
+int vfs_fchown(struct file *file, uid_t user, gid_t group)
+{
+	int error;
+
+	error = mnt_want_write_file(file);
+	if (error)
+		return error;
+	audit_file(file);
+	error = chown_common(&file->f_path, user, group);
+	mnt_drop_write_file(file);
+	return error;
+}
+
+int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
+{
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f))
+		return -EBADF;
+
+	return vfs_fchown(fd_file(f), user, group);
+}
+
+SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
+{
+	return ksys_fchown(fd, user, group);
+}
+
+static inline int file_get_write_access(struct file *f)
+{
+	int error;
+
+	error = get_write_access(f->f_inode);
+	if (unlikely(error))
+		return error;
+	error = mnt_get_write_access(f->f_path.mnt);
+	if (unlikely(error))
+		goto cleanup_inode;
+	if (unlikely(f->f_mode & FMODE_BACKING)) {
+		error = mnt_get_write_access(backing_file_user_path(f)->mnt);
+		if (unlikely(error))
+			goto cleanup_mnt;
+	}
+	return 0;
+
+cleanup_mnt:
+	mnt_put_write_access(f->f_path.mnt);
+cleanup_inode:
+	put_write_access(f->f_inode);
+	return error;
+}
+
+static int do_dentry_open(struct file *f,
+			  int (*open)(struct inode *, struct file *))
+{
+	static const struct file_operations empty_fops = {};
+	struct inode *inode = f->f_path.dentry->d_inode;
+	int error;
+
+	path_get(&f->f_path);
+	f->f_inode = inode;
+	f->f_mapping = inode->i_mapping;
+	f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
+	f->f_sb_err = file_sample_sb_err(f);
+
+	if (unlikely(f->f_flags & O_PATH)) {
+		f->f_mode = FMODE_PATH | FMODE_OPENED;
+		file_set_fsnotify_mode(f, FMODE_NONOTIFY);
+		f->f_op = &empty_fops;
+		return 0;
+	}
+
+	if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
+		i_readcount_inc(inode);
+	} else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
+		error = file_get_write_access(f);
+		if (unlikely(error))
+			goto cleanup_file;
+		f->f_mode |= FMODE_WRITER;
+	}
+
+	/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
+	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
+		f->f_mode |= FMODE_ATOMIC_POS;
+
+	f->f_op = fops_get(inode->i_fop);
+	if (WARN_ON(!f->f_op)) {
+		error = -ENODEV;
+		goto cleanup_all;
+	}
+
+	error = security_file_open(f);
+	if (unlikely(error))
+		goto cleanup_all;
+
+	/*
+	 * Call fsnotify open permission hook and set FMODE_NONOTIFY_* bits
+	 * according to existing permission watches.
+	 * If FMODE_NONOTIFY mode was already set for an fanotify fd or for a
+	 * pseudo file, this call will not change the mode.
+	 */
+	error = fsnotify_open_perm_and_set_mode(f);
+	if (unlikely(error))
+		goto cleanup_all;
+
+	error = break_lease(file_inode(f), f->f_flags);
+	if (unlikely(error))
+		goto cleanup_all;
+
+	/* normally all 3 are set; ->open() can clear them if needed */
+	f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
+	if (!open)
+		open = f->f_op->open;
+	if (open) {
+		error = open(inode, f);
+		if (error)
+			goto cleanup_all;
+	}
+	f->f_mode |= FMODE_OPENED;
+	if ((f->f_mode & FMODE_READ) &&
+	     likely(f->f_op->read || f->f_op->read_iter))
+		f->f_mode |= FMODE_CAN_READ;
+	if ((f->f_mode & FMODE_WRITE) &&
+	     likely(f->f_op->write || f->f_op->write_iter))
+		f->f_mode |= FMODE_CAN_WRITE;
+	if ((f->f_mode & FMODE_LSEEK) && !f->f_op->llseek)
+		f->f_mode &= ~FMODE_LSEEK;
+	if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO)
+		f->f_mode |= FMODE_CAN_ODIRECT;
+
+	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | __O_REGULAR);
+	f->f_iocb_flags = iocb_flags(f);
+
+	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
+
+	if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT))
+		return -EINVAL;
+
+	return 0;
+
+cleanup_all:
+	if (WARN_ON_ONCE(error > 0))
+		error = -EINVAL;
+	fops_put(f->f_op);
+	put_file_access(f);
+cleanup_file:
+	path_put(&f->f_path);
+	f->__f_path.mnt = NULL;
+	f->__f_path.dentry = NULL;
+	f->f_inode = NULL;
+	return error;
+}
+
+/**
+ * finish_open - finish opening a file
+ * @file: file pointer
+ * @dentry: pointer to dentry
+ * @open: open callback
+ *
+ * This can be used to finish opening a file passed to i_op->atomic_open().
+ *
+ * If the open callback is set to NULL, then the standard f_op->open()
+ * filesystem callback is substituted.
+ *
+ * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
+ * the return value of d_splice_alias(), then the caller needs to perform dput()
+ * on it after finish_open().
+ *
+ * Returns zero on success or -errno if the open failed.
+ */
+int finish_open(struct file *file, struct dentry *dentry,
+		int (*open)(struct inode *, struct file *))
+{
+	BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
+
+	file->__f_path.dentry = dentry;
+	return do_dentry_open(file, open);
+}
+EXPORT_SYMBOL(finish_open);
+
+/**
+ * finish_no_open - finish ->atomic_open() without opening the file
+ *
+ * @file: file pointer
+ * @dentry: dentry, ERR_PTR(-E...) or NULL (as returned from ->lookup())
+ *
+ * This can be used to set the result of a lookup in ->atomic_open().
+ *
+ * NB: unlike finish_open() this function does consume the dentry reference and
+ * the caller need not dput() it.
+ *
+ * Returns 0 or -E..., which must be the return value of ->atomic_open() after
+ * having called this function.
+ */
+int finish_no_open(struct file *file, struct dentry *dentry)
+{
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+	file->__f_path.dentry = dentry;
+	return 0;
+}
+EXPORT_SYMBOL(finish_no_open);
+
+char *file_path(struct file *filp, char *buf, int buflen)
+{
+	return d_path(&filp->f_path, buf, buflen);
+}
+EXPORT_SYMBOL(file_path);
+
+/**
+ * vfs_open - open the file at the given path
+ * @path: path to open
+ * @file: newly allocated file with f_flag initialized
+ */
+int vfs_open(const struct path *path, struct file *file)
+{
+	int ret;
+
+	file->__f_path = *path;
+	ret = do_dentry_open(file, NULL);
+	if (!ret) {
+		/*
+		 * Once we return a file with FMODE_OPENED, __fput() will call
+		 * fsnotify_close(), so we need fsnotify_open() here for
+		 * symmetry.
+		 */
+		fsnotify_open(file);
+	}
+	return ret;
+}
+
+struct file *dentry_open(const struct path *path, int flags,
+			 const struct cred *cred)
+{
+	int error;
+	struct file *f;
+
+	/* We must always pass in a valid mount pointer. */
+	BUG_ON(!path->mnt);
+
+	f = alloc_empty_file(flags, cred);
+	if (!IS_ERR(f)) {
+		error = vfs_open(path, f);
+		if (error) {
+			fput(f);
+			f = ERR_PTR(error);
+		}
+	}
+	return f;
+}
+EXPORT_SYMBOL(dentry_open);
+
+struct file *dentry_open_nonotify(const struct path *path, int flags,
+				  const struct cred *cred)
+{
+	struct file *f = alloc_empty_file(flags, cred);
+	if (!IS_ERR(f)) {
+		int error;
+
+		file_set_fsnotify_mode(f, FMODE_NONOTIFY);
+		error = vfs_open(path, f);
+		if (error) {
+			fput(f);
+			f = ERR_PTR(error);
+		}
+	}
+	return f;
+}
+
+/**
+ * kernel_file_open - open a file for kernel internal use
+ * @path:	path of the file to open
+ * @flags:	open flags
+ * @cred:	credentials for open
+ *
+ * Open a file for use by in-kernel consumers. The file is not accounted
+ * against nr_files and must not be installed into the file descriptor
+ * table.
+ *
+ * Return: Opened file on success, an error pointer on failure.
+ */
+struct file *kernel_file_open(const struct path *path, int flags,
+				const struct cred *cred)
+{
+	struct file *f;
+	int error;
+
+	f = alloc_empty_file_noaccount(flags, cred);
+	if (IS_ERR(f))
+		return f;
+
+	error = vfs_open(path, f);
+	if (error) {
+		fput(f);
+		return ERR_PTR(error);
+	}
+	return f;
+}
+EXPORT_SYMBOL_GPL(kernel_file_open);
+
+#define WILL_CREATE(flags)	(flags & (O_CREAT | __O_TMPFILE))
+#define O_PATH_FLAGS		(O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC | O_EMPTYPATH)
+
+inline struct open_how build_open_how(int flags, umode_t mode)
+{
+	struct open_how how = {
+		.flags = flags & VALID_OPEN_FLAGS,
+		.mode = mode & S_IALLUGO,
+	};
+
+	/* O_PATH beats everything else. */
+	if (how.flags & O_PATH)
+		how.flags &= O_PATH_FLAGS;
+	/* Modes should only be set for create-like flags. */
+	if (!WILL_CREATE(how.flags))
+		how.mode = 0;
+	return how;
+}
+
+inline int build_open_flags(const struct open_how *how, struct open_flags *op)
+{
+	u64 flags = how->flags;
+	u64 strip = O_CLOEXEC;
+	int lookup_flags = 0;
+	int acc_mode = ACC_MODE(flags);
+
+	BUILD_BUG_ON_MSG(upper_32_bits(VALID_OPEN_FLAGS),
+			 "VALID_OPEN_FLAGS must fit in 32 bits");
+	/* The whole point: OPENAT2_REGULAR must be unrepresentable in int. */
+	BUILD_BUG_ON_MSG(!upper_32_bits(OPENAT2_REGULAR),
+			 "OPENAT2_REGULAR must live in the upper 32 bits of open_how::flags");
+	/* Prevent a future bit collision between UAPI and internal carrier. */
+	BUILD_BUG_ON_MSG(OPENAT2_REGULAR & VALID_OPEN_FLAGS,
+			 "OPENAT2_REGULAR must not alias any open()/openat() flag");
+	BUILD_BUG_ON_MSG(__O_REGULAR & VALID_OPENAT2_FLAGS,
+			 "__O_REGULAR must not alias any user-visible flag");
+
+	/*
+	 * Strip flags that aren't relevant in determining struct open_flags.
+	 */
+	flags &= ~strip;
+
+	/*
+	 * Older syscalls implicitly clear all of the invalid flags or argument
+	 * values before calling build_open_flags(), but openat2(2) checks all
+	 * of its arguments.
+	 */
+	if (flags & ~VALID_OPENAT2_FLAGS)
+		return -EINVAL;
+	if (how->resolve & ~VALID_RESOLVE_FLAGS)
+		return -EINVAL;
+
+	/* Scoping flags are mutually exclusive. */
+	if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
+		return -EINVAL;
+
+	/* Deal with the mode. */
+	if (WILL_CREATE(flags)) {
+		if (how->mode & ~S_IALLUGO)
+			return -EINVAL;
+		op->mode = how->mode | S_IFREG;
+	} else {
+		if (how->mode != 0)
+			return -EINVAL;
+		op->mode = 0;
+	}
+
+	/*
+	 * Block bugs where O_DIRECTORY | O_CREAT created regular files.
+	 * Note, that blocking O_DIRECTORY | O_CREAT here also protects
+	 * O_TMPFILE below which requires O_DIRECTORY being raised.
+	 */
+	if ((flags & (O_DIRECTORY | O_CREAT)) == (O_DIRECTORY | O_CREAT))
+		return -EINVAL;
+
+	/* Now handle the creative implementation of O_TMPFILE. */
+	if (flags & __O_TMPFILE) {
+		/*
+		 * In order to ensure programs get explicit errors when trying
+		 * to use O_TMPFILE on old kernels we enforce that O_DIRECTORY
+		 * is raised alongside __O_TMPFILE.
+		 */
+		if (!(flags & O_DIRECTORY))
+			return -EINVAL;
+		if (!(acc_mode & MAY_WRITE))
+			return -EINVAL;
+	}
+	/*
+	 * Asking to open a directory and a regular file at the same time is
+	 * contradictory.
+	 */
+	if ((flags & (O_DIRECTORY | OPENAT2_REGULAR)) ==
+	    (O_DIRECTORY | OPENAT2_REGULAR))
+		return -EINVAL;
+
+	if (flags & O_PATH) {
+		/* O_PATH only permits certain other flags to be set. */
+		if (flags & ~O_PATH_FLAGS)
+			return -EINVAL;
+		acc_mode = 0;
+	}
+
+	/*
+	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
+	 * check for O_DSYNC if the need any syncing at all we enforce it's
+	 * always set instead of having to deal with possibly weird behaviour
+	 * for malicious applications setting only __O_SYNC.
+	 */
+	if (flags & __O_SYNC)
+		flags |= O_DSYNC;
+
+	/*
+	 * Translate the upper-32-bit UAPI bit OPENAT2_REGULAR into the
+	 * kernel-internal lower-32-bit __O_REGULAR carrier so the bit
+	 * survives the assignment to op->open_flag (an int) below and the
+	 * subsequent flow through f->f_flags (unsigned int) and the
+	 * i_op->atomic_open() callback (unsigned). do_dentry_open() strips
+	 * __O_REGULAR before the file becomes visible to userspace.
+	 */
+	if (flags & OPENAT2_REGULAR) {
+		flags &= ~OPENAT2_REGULAR;
+		flags |= __O_REGULAR;
+	}
+
+	op->open_flag = flags;
+
+	/* O_TRUNC implies we need access checks for write permissions */
+	if (flags & O_TRUNC)
+		acc_mode |= MAY_WRITE;
+
+	/* Allow the LSM permission hook to distinguish append
+	   access from general write access. */
+	if (flags & O_APPEND)
+		acc_mode |= MAY_APPEND;
+
+	op->acc_mode = acc_mode;
+
+	op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
+
+	if (flags & O_CREAT) {
+		op->intent |= LOOKUP_CREATE;
+		if (flags & O_EXCL) {
+			op->intent |= LOOKUP_EXCL;
+			flags |= O_NOFOLLOW;
+		}
+	}
+
+	if (flags & O_DIRECTORY)
+		lookup_flags |= LOOKUP_DIRECTORY;
+	if (!(flags & O_NOFOLLOW))
+		lookup_flags |= LOOKUP_FOLLOW;
+	if (flags & O_EMPTYPATH)
+		lookup_flags |= LOOKUP_EMPTY;
+
+	if (how->resolve & RESOLVE_NO_XDEV)
+		lookup_flags |= LOOKUP_NO_XDEV;
+	if (how->resolve & RESOLVE_NO_MAGICLINKS)
+		lookup_flags |= LOOKUP_NO_MAGICLINKS;
+	if (how->resolve & RESOLVE_NO_SYMLINKS)
+		lookup_flags |= LOOKUP_NO_SYMLINKS;
+	if (how->resolve & RESOLVE_BENEATH)
+		lookup_flags |= LOOKUP_BENEATH;
+	if (how->resolve & RESOLVE_IN_ROOT)
+		lookup_flags |= LOOKUP_IN_ROOT;
+	if (how->resolve & RESOLVE_CACHED) {
+		/* Don't bother even trying for create/truncate/tmpfile open */
+		if (flags & (O_TRUNC | O_CREAT | __O_TMPFILE))
+			return -EAGAIN;
+		lookup_flags |= LOOKUP_CACHED;
+	}
+
+	op->lookup_flags = lookup_flags;
+	return 0;
+}
+
+/**
+ * file_open_name - open file and return file pointer
+ *
+ * @name:	struct filename containing path to open
+ * @flags:	open flags as per the open(2) second argument
+ * @mode:	mode for the new file if O_CREAT is set, else ignored
+ *
+ * This is the helper to open a file from kernelspace if you really
+ * have to.  But in generally you should not do this, so please move
+ * along, nothing to see here..
+ */
+struct file *file_open_name(struct filename *name, int flags, umode_t mode)
+{
+	struct open_flags op;
+	struct open_how how = build_open_how(flags, mode);
+	int err = build_open_flags(&how, &op);
+	if (err)
+		return ERR_PTR(err);
+	return do_file_open(AT_FDCWD, name, &op);
+}
+
+/**
+ * filp_open - open file and return file pointer
+ *
+ * @filename:	path to open
+ * @flags:	open flags as per the open(2) second argument
+ * @mode:	mode for the new file if O_CREAT is set, else ignored
+ *
+ * This is the helper to open a file from kernelspace if you really
+ * have to.  But in generally you should not do this, so please move
+ * along, nothing to see here..
+ */
+struct file *filp_open(const char *filename, int flags, umode_t mode)
+{
+	CLASS(filename_kernel, name)(filename);
+	return file_open_name(name, flags, mode);
+}
+EXPORT_SYMBOL(filp_open);
+
+struct file *file_open_root(const struct path *root,
+			    const char *filename, int flags, umode_t mode)
+{
+	struct open_flags op;
+	struct open_how how = build_open_how(flags, mode);
+	int err = build_open_flags(&how, &op);
+	if (err)
+		return ERR_PTR(err);
+	return do_file_open_root(root, filename, &op);
+}
+EXPORT_SYMBOL(file_open_root);
+
+static int do_sys_openat2(int dfd, const char __user *filename,
+			  struct open_how *how)
+{
+	struct open_flags op;
+	int err = build_open_flags(how, &op);
+	if (unlikely(err))
+		return err;
+
+	CLASS(filename_flags, name)(filename, op.lookup_flags);
+	return FD_ADD(how->flags, do_file_open(dfd, name, &op));
+}
+
+int do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
+{
+	struct open_how how = build_open_how(flags, mode);
+	return do_sys_openat2(dfd, filename, &how);
+}
+
+
+SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
+{
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
+	return do_sys_open(AT_FDCWD, filename, flags, mode);
+}
+
+SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
+		umode_t, mode)
+{
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
+	return do_sys_open(dfd, filename, flags, mode);
+}
+
+SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
+		struct open_how __user *, how, size_t, usize)
+{
+	int err;
+	struct open_how tmp;
+
+	BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
+	BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
+
+	if (unlikely(usize < OPEN_HOW_SIZE_VER0))
+		return -EINVAL;
+	if (unlikely(usize > PAGE_SIZE))
+		return -E2BIG;
+
+	err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
+	if (err)
+		return err;
+
+	audit_openat2_how(&tmp);
+
+	/* O_LARGEFILE is only allowed for non-O_PATH. */
+	if (!(tmp.flags & O_PATH) && force_o_largefile())
+		tmp.flags |= O_LARGEFILE;
+
+	return do_sys_openat2(dfd, filename, &tmp);
+}
+
+#ifdef CONFIG_COMPAT
+/*
+ * Exactly like sys_open(), except that it doesn't set the
+ * O_LARGEFILE flag.
+ */
+COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
+{
+	return do_sys_open(AT_FDCWD, filename, flags, mode);
+}
+
+/*
+ * Exactly like sys_openat(), except that it doesn't set the
+ * O_LARGEFILE flag.
+ */
+COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
+{
+	return do_sys_open(dfd, filename, flags, mode);
+}
+#endif
+
+#ifndef __alpha__
+
+/*
+ * For backward compatibility?  Maybe this should be moved
+ * into arch/i386 instead?
+ */
+SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
+{
+	int flags = O_CREAT | O_WRONLY | O_TRUNC;
+
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
+	return do_sys_open(AT_FDCWD, pathname, flags, mode);
+}
+#endif
+
+/*
+ * "id" is the POSIX thread ID. We use the
+ * files pointer for this..
+ */
+static int filp_flush(struct file *filp, fl_owner_t id)
+{
+	int retval = 0;
+
+	if (CHECK_DATA_CORRUPTION(file_count(filp) == 0, filp,
+			"VFS: Close: file count is 0 (f_op=%ps)",
+			filp->f_op)) {
+		return 0;
+	}
+
+	if (filp->f_op->flush)
+		retval = filp->f_op->flush(filp, id);
+
+	if (likely(!(filp->f_mode & FMODE_PATH))) {
+		dnotify_flush(filp, id);
+		locks_remove_posix(filp, id);
+	}
+	return retval;
+}
+
+int filp_close(struct file *filp, fl_owner_t id)
+{
+	int retval;
+
+	retval = filp_flush(filp, id);
+	fput_close(filp);
+
+	return retval;
+}
+EXPORT_SYMBOL(filp_close);
+
+/*
+ * Careful here! We test whether the file pointer is NULL before
+ * releasing the fd. This ensures that one clone task can't release
+ * an fd while another clone is opening it.
+ */
+SYSCALL_DEFINE1(close, unsigned int, fd)
+{
+	int retval;
+	struct file *file;
+
+	file = file_close_fd(fd);
+	if (!file)
+		return -EBADF;
+
+	retval = filp_flush(file, current->files);
+
+	/*
+	 * We're returning to user space. Don't bother
+	 * with any delayed fput() cases.
+	 */
+	fput_close_sync(file);
+
+	if (likely(retval == 0))
+		return 0;
+
+	/* can't restart close syscall because file table entry was cleared */
+	if (retval == -ERESTARTSYS ||
+	    retval == -ERESTARTNOINTR ||
+	    retval == -ERESTARTNOHAND ||
+	    retval == -ERESTART_RESTARTBLOCK)
+		retval = -EINTR;
+
+	return retval;
+}
+
+/*
+ * This routine simulates a hangup on the tty, to arrange that users
+ * are given clean terminals at login time.
+ */
+SYSCALL_DEFINE0(vhangup)
+{
+	if (capable(CAP_SYS_TTY_CONFIG)) {
+		tty_vhangup_self();
+		return 0;
+	}
+	return -EPERM;
+}
+
+/*
+ * Called when an inode is about to be open.
+ * We use this to disallow opening large files on 32bit systems if
+ * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
+ * on this flag in sys_open.
+ */
+int generic_file_open(struct inode * inode, struct file * filp)
+{
+	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
+		return -EOVERFLOW;
+	return 0;
+}
+
+EXPORT_SYMBOL(generic_file_open);
+
+/*
+ * This is used by subsystems that don't want seekable
+ * file descriptors. The function is not supposed to ever fail, the only
+ * reason it returns an 'int' and not 'void' is so that it can be plugged
+ * directly into file_operations structure.
+ */
+int nonseekable_open(struct inode *inode, struct file *filp)
+{
+	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+	return 0;
+}
+
+EXPORT_SYMBOL(nonseekable_open);
+
+/*
+ * stream_open is used by subsystems that want stream-like file descriptors.
+ * Such file descriptors are not seekable and don't have notion of position
+ * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
+ * Contrary to file descriptors of other regular files, .read() and .write()
+ * can run simultaneously.
+ *
+ * stream_open never fails and is marked to return int so that it could be
+ * directly used as file_operations.open .
+ */
+int stream_open(struct inode *inode, struct file *filp)
+{
+	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
+	filp->f_mode |= FMODE_STREAM;
+	return 0;
+}
+
+EXPORT_SYMBOL(stream_open);