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, 61 insertions, 0 deletions

diff --git a/fs/befs/io.c b/fs/befs/io.c
new file mode 100644
index 000000000..2caf50a4a
--- /dev/null
+++ b/fs/befs/io.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/befs/io.c
+ *
+ * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com
+ *
+ * Based on portions of file.c and inode.c
+ * by Makoto Kato (m_kato@ga2.so-net.ne.jp)
+ *
+ * Many thanks to Dominic Giampaolo, author of Practical File System
+ * Design with the Be File System, for such a helpful book.
+ *
+ */
+
+#include <linux/buffer_head.h>
+
+#include "befs.h"
+#include "io.h"
+
+/*
+ * Converts befs notion of disk addr to a disk offset and uses
+ * linux kernel function sb_bread() to get the buffer containing
+ * the offset.
+ */
+
+struct buffer_head *
+befs_bread_iaddr(struct super_block *sb, befs_inode_addr iaddr)
+{
+	struct buffer_head *bh;
+	befs_blocknr_t block;
+	struct befs_sb_info *befs_sb = BEFS_SB(sb);
+
+	befs_debug(sb, "---> Enter %s "
+		   "[%u, %hu, %hu]", __func__, iaddr.allocation_group,
+		   iaddr.start, iaddr.len);
+
+	if (iaddr.allocation_group > befs_sb->num_ags) {
+		befs_error(sb, "BEFS: Invalid allocation group %u, max is %u",
+			   iaddr.allocation_group, befs_sb->num_ags);
+		goto error;
+	}
+
+	block = iaddr2blockno(sb, &iaddr);
+
+	befs_debug(sb, "%s: offset = %lu", __func__, (unsigned long)block);
+
+	bh = sb_bread(sb, block);
+
+	if (bh == NULL) {
+		befs_error(sb, "Failed to read block %lu",
+			   (unsigned long)block);
+		goto error;
+	}
+
+	befs_debug(sb, "<--- %s", __func__);
+	return bh;
+
+error:
+	befs_debug(sb, "<--- %s ERROR", __func__);
+	return NULL;
+}