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, 94 insertions, 0 deletions

diff --git a/fs/smb/client/cifsroot.c b/fs/smb/client/cifsroot.c
new file mode 100644
index 000000000..56ec1b233
--- /dev/null
+++ b/fs/smb/client/cifsroot.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SMB root file system support
+ *
+ * Copyright (c) 2019 Paulo Alcantara <palcantara@suse.de>
+ */
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/ctype.h>
+#include <linux/string.h>
+#include <linux/root_dev.h>
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <net/ipconfig.h>
+
+#define DEFAULT_MNT_OPTS \
+	"vers=1.0,cifsacl,mfsymlinks,rsize=1048576,wsize=65536,uid=0,gid=0," \
+	"hard,rootfs"
+
+static char root_dev[2048] __initdata = "";
+static char root_opts[1024] __initdata = DEFAULT_MNT_OPTS;
+
+static __be32 __init parse_srvaddr(char *start, char *end)
+{
+	/* TODO: ipv6 support */
+	char addr[sizeof("aaa.bbb.ccc.ddd")];
+	int i = 0;
+
+	while (start < end && i < sizeof(addr) - 1) {
+		if (isdigit(*start) || *start == '.')
+			addr[i++] = *start;
+		start++;
+	}
+	addr[i] = '\0';
+	return in_aton(addr);
+}
+
+/* cifsroot=//<server-ip>/<share>[,options] */
+static int __init cifs_root_setup(char *line)
+{
+	char *s;
+	int len;
+	__be32 srvaddr = htonl(INADDR_NONE);
+
+	ROOT_DEV = Root_CIFS;
+
+	if (strlen(line) > 3 && line[0] == '/' && line[1] == '/') {
+		s = strchr(&line[2], '/');
+		if (!s || s[1] == '\0')
+			return 1;
+
+		/* make s point to ',' or '\0' at end of line */
+		s = strchrnul(s, ',');
+		/* len is strlen(unc) + '\0' */
+		len = s - line + 1;
+		if (len > sizeof(root_dev)) {
+			pr_err("Root-CIFS: UNC path too long\n");
+			return 1;
+		}
+		strscpy(root_dev, line, len);
+		srvaddr = parse_srvaddr(&line[2], s);
+		if (*s) {
+			int n = snprintf(root_opts,
+					 sizeof(root_opts), "%s,%s",
+					 DEFAULT_MNT_OPTS, s + 1);
+			if (n >= sizeof(root_opts)) {
+				pr_err("Root-CIFS: mount options string too long\n");
+				root_opts[sizeof(root_opts)-1] = '\0';
+				return 1;
+			}
+		}
+	}
+
+	root_server_addr = srvaddr;
+
+	return 1;
+}
+
+__setup("cifsroot=", cifs_root_setup);
+
+int __init cifs_root_data(char **dev, char **opts)
+{
+	if (!root_dev[0] || root_server_addr == htonl(INADDR_NONE)) {
+		pr_err("Root-CIFS: no SMB server address\n");
+		return -1;
+	}
+
+	*dev = root_dev;
+	*opts = root_opts;
+
+	return 0;
+}