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, 69 insertions, 0 deletions

diff --git a/fs/smb/client/unc.c b/fs/smb/client/unc.c
new file mode 100644
index 000000000..f6fc5e343
--- /dev/null
+++ b/fs/smb/client/unc.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) 2020, Microsoft Corporation.
+ *
+ *   Author(s): Steve French <stfrench@microsoft.com>
+ *              Suresh Jayaraman <sjayaraman@suse.de>
+ *              Jeff Layton <jlayton@kernel.org>
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/inet.h>
+#include <linux/ctype.h>
+#include "cifsglob.h"
+#include "cifsproto.h"
+
+/* extract the host portion of the UNC string */
+char *extract_hostname(const char *unc)
+{
+	const char *src;
+	char *dst, *delim;
+	unsigned int len;
+
+	/* skip double chars at beginning of string */
+	/* BB: check validity of these bytes? */
+	if (strlen(unc) < 3)
+		return ERR_PTR(-EINVAL);
+	for (src = unc; *src && *src == '\\'; src++)
+		;
+	if (!*src)
+		return ERR_PTR(-EINVAL);
+
+	/* delimiter between hostname and sharename is always '\\' now */
+	delim = strchr(src, '\\');
+	if (!delim)
+		return ERR_PTR(-EINVAL);
+
+	len = delim - src;
+	dst = kmalloc((len + 1), GFP_KERNEL);
+	if (dst == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(dst, src, len);
+	dst[len] = '\0';
+
+	return dst;
+}
+
+char *extract_sharename(const char *unc)
+{
+	const char *src;
+	char *delim, *dst;
+
+	/* skip double chars at the beginning */
+	src = unc + 2;
+
+	/* share name is always preceded by '\\' now */
+	delim = strchr(src, '\\');
+	if (!delim)
+		return ERR_PTR(-EINVAL);
+	delim++;
+
+	/* caller has to free the memory */
+	dst = kstrdup(delim, GFP_KERNEL);
+	if (!dst)
+		return ERR_PTR(-ENOMEM);
+
+	return dst;
+}