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, 180 insertions, 0 deletions

diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c
new file mode 100644
index 000000000..bdb587a72
--- /dev/null
+++ b/net/sunrpc/sysctl.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/net/sunrpc/sysctl.c
+ *
+ * Sysctl interface to sunrpc module.
+ *
+ * I would prefer to register the sunrpc table below sys/net, but that's
+ * impossible at the moment.
+ */
+
+#include <linux/types.h>
+#include <linux/linkage.h>
+#include <linux/ctype.h>
+#include <linux/fs.h>
+#include <linux/sysctl.h>
+#include <linux/module.h>
+
+#include <linux/uaccess.h>
+#include <linux/sunrpc/types.h>
+#include <linux/sunrpc/sched.h>
+#include <linux/sunrpc/stats.h>
+#include <linux/sunrpc/svc_xprt.h>
+
+#include "netns.h"
+
+/*
+ * Declare the debug flags here
+ */
+unsigned int	rpc_debug;
+EXPORT_SYMBOL_GPL(rpc_debug);
+
+unsigned int	nfs_debug;
+EXPORT_SYMBOL_GPL(nfs_debug);
+
+unsigned int	nfsd_debug;
+EXPORT_SYMBOL_GPL(nfsd_debug);
+
+unsigned int	nlm_debug;
+EXPORT_SYMBOL_GPL(nlm_debug);
+
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
+
+static int proc_do_xprt(const struct ctl_table *table, int write,
+			void *buffer, size_t *lenp, loff_t *ppos)
+{
+	char tmpbuf[256];
+	ssize_t len;
+
+	if (write || *ppos) {
+		*lenp = 0;
+		return 0;
+	}
+	len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
+	len = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
+
+	if (len < 0) {
+		*lenp = 0;
+		return -EINVAL;
+	}
+	*lenp = len;
+	return 0;
+}
+
+static int
+proc_dodebug(const struct ctl_table *table, int write, void *buffer, size_t *lenp,
+	     loff_t *ppos)
+{
+	char		tmpbuf[20], *s = NULL;
+	char *p;
+	unsigned int	value;
+	size_t		left, len;
+
+	if ((*ppos && !write) || !*lenp) {
+		*lenp = 0;
+		return 0;
+	}
+
+	left = *lenp;
+
+	if (write) {
+		p = buffer;
+		while (left && isspace(*p)) {
+			left--;
+			p++;
+		}
+		if (!left)
+			goto done;
+
+		if (left > sizeof(tmpbuf) - 1)
+			return -EINVAL;
+		memcpy(tmpbuf, p, left);
+		tmpbuf[left] = '\0';
+
+		value = simple_strtol(tmpbuf, &s, 0);
+		if (s) {
+			left -= (s - tmpbuf);
+			if (left && !isspace(*s))
+				return -EINVAL;
+			while (left && isspace(*s)) {
+				left--;
+				s++;
+			}
+		} else
+			left = 0;
+		*(unsigned int *) table->data = value;
+		/* Display the RPC tasks on writing to rpc_debug */
+		if (strcmp(table->procname, "rpc_debug") == 0)
+			rpc_show_tasks(&init_net);
+	} else {
+		len = sprintf(tmpbuf, "0x%04x", *(unsigned int *) table->data);
+		if (len > left)
+			len = left;
+		memcpy(buffer, tmpbuf, len);
+		if ((left -= len) > 0) {
+			*((char *)buffer + len) = '\n';
+			left--;
+		}
+	}
+
+done:
+	*lenp -= left;
+	*ppos += *lenp;
+	return 0;
+}
+
+static struct ctl_table_header *sunrpc_table_header;
+
+static struct ctl_table debug_table[] = {
+	{
+		.procname	= "rpc_debug",
+		.data		= &rpc_debug,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dodebug
+	},
+	{
+		.procname	= "nfs_debug",
+		.data		= &nfs_debug,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dodebug
+	},
+	{
+		.procname	= "nfsd_debug",
+		.data		= &nfsd_debug,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dodebug
+	},
+	{
+		.procname	= "nlm_debug",
+		.data		= &nlm_debug,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dodebug
+	},
+	{
+		.procname	= "transports",
+		.maxlen		= 256,
+		.mode		= 0444,
+		.proc_handler	= proc_do_xprt,
+	},
+};
+
+void
+rpc_register_sysctl(void)
+{
+	if (!sunrpc_table_header)
+		sunrpc_table_header = register_sysctl("sunrpc", debug_table);
+}
+
+void
+rpc_unregister_sysctl(void)
+{
+	if (sunrpc_table_header) {
+		unregister_sysctl_table(sunrpc_table_header);
+		sunrpc_table_header = NULL;
+	}
+}
+#endif