ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 176 insertions, 0 deletions

diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
new file mode 100644
index 000000000..2999c2cc8
--- /dev/null
+++ b/fs/ext4/fsync.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/ext4/fsync.c
+ *
+ *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
+ *  from
+ *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
+ *                      Laboratoire MASI - Institut Blaise Pascal
+ *                      Universite Pierre et Marie Curie (Paris VI)
+ *  from
+ *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  ext4fs fsync primitive
+ *
+ *  Big-endian to little-endian byte-swapping/bitmaps by
+ *        David S. Miller (davem@caip.rutgers.edu), 1995
+ *
+ *  Removed unnecessary code duplication for little endian machines
+ *  and excessive __inline__s.
+ *        Andi Kleen, 1997
+ *
+ * Major simplications and cleanup - we only need to do the metadata, because
+ * we can depend on generic_block_fdatasync() to sync the data blocks.
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+
+#include "ext4.h"
+#include "ext4_jbd2.h"
+
+#include <trace/events/ext4.h>
+
+/*
+ * If we're not journaling and this is a just-created file, we have to
+ * sync our parent directory (if it was freshly created) since
+ * otherwise it will only be written by writeback, leaving a huge
+ * window during which a crash may lose the file.  This may apply for
+ * the parent directory's parent as well, and so on recursively, if
+ * they are also freshly created.
+ */
+static int ext4_sync_parent(struct inode *inode)
+{
+	struct dentry *dentry, *next;
+	int ret = 0;
+
+	if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
+		return 0;
+	dentry = d_find_any_alias(inode);
+	if (!dentry)
+		return 0;
+	while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
+		ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
+
+		next = dget_parent(dentry);
+		dput(dentry);
+		dentry = next;
+		inode = dentry->d_inode;
+
+		/*
+		 * The directory inode may have gone through rmdir by now. But
+		 * the inode itself and its blocks are still allocated (we hold
+		 * a reference to the inode via its dentry), so it didn't go
+		 * through ext4_evict_inode()) and so we are safe to flush
+		 * metadata blocks and the inode.
+		 */
+		ret = sync_inode_metadata(inode, 1);
+		if (ret)
+			break;
+	}
+	dput(dentry);
+	return ret;
+}
+
+static int ext4_fsync_nojournal(struct file *file, loff_t start, loff_t end,
+				int datasync, bool *needs_barrier)
+{
+	struct inode *inode = file->f_inode;
+	int ret;
+
+	ret = sync_inode_metadata(inode, 1);
+	if (ret)
+		return ret;
+	ret = ext4_sync_parent(inode);
+
+	if (test_opt(inode->i_sb, BARRIER))
+		*needs_barrier = true;
+
+	return ret;
+}
+
+static int ext4_fsync_journal(struct inode *inode, bool datasync,
+			     bool *needs_barrier)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
+	tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
+
+	/*
+	 * Fastcommit does not really support fsync on directories or other
+	 * special files. Force a full commit.
+	 */
+	if (!S_ISREG(inode->i_mode))
+		return ext4_force_commit(inode->i_sb);
+
+	if (journal->j_flags & JBD2_BARRIER &&
+	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
+		*needs_barrier = true;
+
+	return ext4_fc_commit(journal, commit_tid);
+}
+
+/*
+ * akpm: A new design for ext4_sync_file().
+ *
+ * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
+ * There cannot be a transaction open by this task.
+ * Another task could have dirtied this inode.  Its data can be in any
+ * state in the journalling system.
+ *
+ * What we do is just kick off a commit and wait on it.  This will snapshot the
+ * inode to disk.
+ */
+int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	int ret = 0, err;
+	bool needs_barrier = false;
+	struct inode *inode = file->f_mapping->host;
+
+	ret = ext4_emergency_state(inode->i_sb);
+	if (unlikely(ret))
+		return ret;
+
+	ASSERT(ext4_journal_current_handle() == NULL);
+
+	trace_ext4_sync_file_enter(file, datasync);
+
+	if (sb_rdonly(inode->i_sb))
+		goto out;
+
+	ret = file_write_and_wait_range(file, start, end);
+	if (ret)
+		goto out;
+
+	if (!EXT4_SB(inode->i_sb)->s_journal) {
+		ret = ext4_fsync_nojournal(file, start, end, datasync,
+					   &needs_barrier);
+		if (needs_barrier)
+			goto issue_flush;
+		goto out;
+	}
+
+	/*
+	 *  The caller's filemap_fdatawrite()/wait will sync the data.
+	 *  Metadata is in the journal, we wait for proper transaction to
+	 *  commit here.
+	 */
+	ret = ext4_fsync_journal(inode, datasync, &needs_barrier);
+
+issue_flush:
+	if (needs_barrier) {
+		err = blkdev_issue_flush(inode->i_sb->s_bdev);
+		if (!ret)
+			ret = err;
+	}
+out:
+	err = file_check_and_advance_wb_err(file);
+	if (ret == 0)
+		ret = err;
+	trace_ext4_sync_file_exit(inode, ret);
+	return ret;
+}