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, 284 insertions, 0 deletions

diff --git a/fs/qnx6/dir.c b/fs/qnx6/dir.c
new file mode 100644
index 000000000..56bbaffe4
--- /dev/null
+++ b/fs/qnx6/dir.c
@@ -0,0 +1,284 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QNX6 file system, Linux implementation.
+ *
+ * Version : 1.0.0
+ *
+ * History :
+ *
+ * 01-02-2012 by Kai Bankett (chaosman@ontika.net) : first release.
+ * 16-02-2012 pagemap extension by Al Viro
+ *
+ */
+
+#include <linux/filelock.h>
+#include "qnx6.h"
+
+static unsigned qnx6_lfile_checksum(char *name, unsigned size)
+{
+	unsigned crc = 0;
+	char *end = name + size;
+	while (name < end) {
+		crc = ((crc >> 1) + *(name++)) ^
+			((crc & 0x00000001) ? 0x80000000 : 0);
+	}
+	return crc;
+}
+
+static void *qnx6_get_folio(struct inode *dir, unsigned long n,
+		struct folio **foliop)
+{
+	struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);
+
+	if (IS_ERR(folio))
+		return folio;
+	*foliop = folio;
+	return kmap_local_folio(folio, 0);
+}
+
+static unsigned last_entry(struct inode *inode, unsigned long page_nr)
+{
+	unsigned long last_byte = inode->i_size;
+	last_byte -= page_nr << PAGE_SHIFT;
+	if (last_byte > PAGE_SIZE)
+		last_byte = PAGE_SIZE;
+	return last_byte / QNX6_DIR_ENTRY_SIZE;
+}
+
+static struct qnx6_long_filename *qnx6_longname(struct super_block *sb,
+					 struct qnx6_long_dir_entry *de,
+					 struct folio **foliop)
+{
+	struct qnx6_sb_info *sbi = QNX6_SB(sb);
+	u32 s = fs32_to_cpu(sbi, de->de_long_inode); /* in block units */
+	u32 n = s >> (PAGE_SHIFT - sb->s_blocksize_bits); /* in pages */
+	u32 offs;
+	struct address_space *mapping = sbi->longfile->i_mapping;
+	struct folio *folio = read_mapping_folio(mapping, n, NULL);
+
+	if (IS_ERR(folio))
+		return ERR_CAST(folio);
+	offs = offset_in_folio(folio, s << sb->s_blocksize_bits);
+	*foliop = folio;
+	return kmap_local_folio(folio, offs);
+}
+
+static int qnx6_dir_longfilename(struct inode *inode,
+			struct qnx6_long_dir_entry *de,
+			struct dir_context *ctx,
+			unsigned de_inode)
+{
+	struct qnx6_long_filename *lf;
+	struct super_block *s = inode->i_sb;
+	struct qnx6_sb_info *sbi = QNX6_SB(s);
+	struct folio *folio;
+	int lf_size;
+
+	if (de->de_size != 0xff) {
+		/* error - long filename entries always have size 0xff
+		   in direntry */
+		pr_err("invalid direntry size (%i).\n", de->de_size);
+		return 0;
+	}
+	lf = qnx6_longname(s, de, &folio);
+	if (IS_ERR(lf)) {
+		pr_err("Error reading longname\n");
+		return 0;
+	}
+
+	lf_size = fs16_to_cpu(sbi, lf->lf_size);
+
+	if (lf_size > QNX6_LONG_NAME_MAX) {
+		pr_debug("file %s\n", lf->lf_fname);
+		pr_err("Filename too long (%i)\n", lf_size);
+		folio_release_kmap(folio, lf);
+		return 0;
+	}
+
+	/* calc & validate longfilename checksum
+	   mmi 3g filesystem does not have that checksum */
+	if (!test_opt(s, MMI_FS) && fs32_to_cpu(sbi, de->de_checksum) !=
+			qnx6_lfile_checksum(lf->lf_fname, lf_size))
+		pr_info("long filename checksum error.\n");
+
+	pr_debug("qnx6_readdir:%.*s inode:%u\n",
+		 lf_size, lf->lf_fname, de_inode);
+	if (!dir_emit(ctx, lf->lf_fname, lf_size, de_inode, DT_UNKNOWN)) {
+		folio_release_kmap(folio, lf);
+		return 0;
+	}
+
+	folio_release_kmap(folio, lf);
+	/* success */
+	return 1;
+}
+
+static int qnx6_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	struct super_block *s = inode->i_sb;
+	struct qnx6_sb_info *sbi = QNX6_SB(s);
+	loff_t pos = ctx->pos & ~(QNX6_DIR_ENTRY_SIZE - 1);
+	unsigned long npages = dir_pages(inode);
+	unsigned long n = pos >> PAGE_SHIFT;
+	unsigned offset = (pos & ~PAGE_MASK) / QNX6_DIR_ENTRY_SIZE;
+	bool done = false;
+
+	ctx->pos = pos;
+	if (ctx->pos >= inode->i_size)
+		return 0;
+
+	for ( ; !done && n < npages; n++, offset = 0) {
+		struct qnx6_dir_entry *de;
+		struct folio *folio;
+		char *kaddr = qnx6_get_folio(inode, n, &folio);
+		struct qnx6_dir_entry *limit;
+
+		if (IS_ERR(kaddr)) {
+			pr_err("%s(): read failed\n", __func__);
+			ctx->pos = (n + 1) << PAGE_SHIFT;
+			return PTR_ERR(kaddr);
+		}
+		de = (struct qnx6_dir_entry *)kaddr + offset;
+		limit = (struct qnx6_dir_entry *)kaddr + last_entry(inode, n);
+		for (; de < limit; de++, ctx->pos += QNX6_DIR_ENTRY_SIZE) {
+			int size = de->de_size;
+			u32 no_inode = fs32_to_cpu(sbi, de->de_inode);
+
+			if (!no_inode || !size)
+				continue;
+
+			if (size > QNX6_SHORT_NAME_MAX) {
+				/* long filename detected
+				   get the filename from long filename
+				   structure / block */
+				if (!qnx6_dir_longfilename(inode,
+					(struct qnx6_long_dir_entry *)de,
+					ctx, no_inode)) {
+					done = true;
+					break;
+				}
+			} else {
+				pr_debug("%s():%.*s inode:%u\n",
+					 __func__, size, de->de_fname,
+					 no_inode);
+				if (!dir_emit(ctx, de->de_fname, size,
+				      no_inode, DT_UNKNOWN)) {
+					done = true;
+					break;
+				}
+			}
+		}
+		folio_release_kmap(folio, kaddr);
+	}
+	return 0;
+}
+
+/*
+ * check if the long filename is correct.
+ */
+static unsigned qnx6_long_match(int len, const char *name,
+			struct qnx6_long_dir_entry *de, struct inode *dir)
+{
+	struct super_block *s = dir->i_sb;
+	struct qnx6_sb_info *sbi = QNX6_SB(s);
+	struct folio *folio;
+	int thislen;
+	struct qnx6_long_filename *lf = qnx6_longname(s, de, &folio);
+
+	if (IS_ERR(lf))
+		return 0;
+
+	thislen = fs16_to_cpu(sbi, lf->lf_size);
+	if (len != thislen) {
+		folio_release_kmap(folio, lf);
+		return 0;
+	}
+	if (memcmp(name, lf->lf_fname, len) == 0) {
+		folio_release_kmap(folio, lf);
+		return fs32_to_cpu(sbi, de->de_inode);
+	}
+	folio_release_kmap(folio, lf);
+	return 0;
+}
+
+/*
+ * check if the filename is correct.
+ */
+static unsigned qnx6_match(struct super_block *s, int len, const char *name,
+			struct qnx6_dir_entry *de)
+{
+	struct qnx6_sb_info *sbi = QNX6_SB(s);
+	if (memcmp(name, de->de_fname, len) == 0)
+		return fs32_to_cpu(sbi, de->de_inode);
+	return 0;
+}
+
+
+unsigned qnx6_find_ino(int len, struct inode *dir, const char *name)
+{
+	struct super_block *s = dir->i_sb;
+	struct qnx6_inode_info *ei = QNX6_I(dir);
+	struct folio *folio;
+	unsigned long start, n;
+	unsigned long npages = dir_pages(dir);
+	unsigned ino;
+	struct qnx6_dir_entry *de;
+	struct qnx6_long_dir_entry *lde;
+
+	if (npages == 0)
+		return 0;
+	start = ei->i_dir_start_lookup;
+	if (start >= npages)
+		start = 0;
+	n = start;
+
+	do {
+		de = qnx6_get_folio(dir, n, &folio);
+		if (!IS_ERR(de)) {
+			int limit = last_entry(dir, n);
+			int i;
+
+			for (i = 0; i < limit; i++, de++) {
+				if (len <= QNX6_SHORT_NAME_MAX) {
+					/* short filename */
+					if (len != de->de_size)
+						continue;
+					ino = qnx6_match(s, len, name, de);
+					if (ino)
+						goto found;
+				} else if (de->de_size == 0xff) {
+					/* deal with long filename */
+					lde = (struct qnx6_long_dir_entry *)de;
+					ino = qnx6_long_match(len,
+								name, lde, dir);
+					if (ino)
+						goto found;
+				} else
+					pr_err("undefined filename size in inode.\n");
+			}
+			folio_release_kmap(folio, de - i);
+		}
+
+		if (++n >= npages)
+			n = 0;
+	} while (n != start);
+	return 0;
+
+found:
+	ei->i_dir_start_lookup = n;
+	folio_release_kmap(folio, de);
+	return ino;
+}
+
+const struct file_operations qnx6_dir_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= qnx6_readdir,
+	.fsync		= simple_fsync,
+	.setlease	= generic_setlease,
+};
+
+const struct inode_operations qnx6_dir_inode_operations = {
+	.lookup		= qnx6_lookup,
+};