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, 90 insertions, 0 deletions

diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c
new file mode 100644
index 000000000..ad40762a8
--- /dev/null
+++ b/net/ipv4/metrics.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/netlink.h>
+#include <linux/nospec.h>
+#include <linux/rtnetlink.h>
+#include <linux/types.h>
+#include <net/ip.h>
+#include <net/net_namespace.h>
+#include <net/tcp.h>
+
+static int ip_metrics_convert(struct nlattr *fc_mx,
+			      int fc_mx_len, u32 *metrics,
+			      struct netlink_ext_ack *extack)
+{
+	bool ecn_ca = false;
+	struct nlattr *nla;
+	int remaining;
+
+	nla_for_each_attr(nla, fc_mx, fc_mx_len, remaining) {
+		int type = nla_type(nla);
+		u32 val;
+
+		if (!type)
+			continue;
+		if (type > RTAX_MAX) {
+			NL_SET_ERR_MSG(extack, "Invalid metric type");
+			return -EINVAL;
+		}
+
+		type = array_index_nospec(type, RTAX_MAX + 1);
+		if (type == RTAX_CC_ALGO) {
+			char tmp[TCP_CA_NAME_MAX];
+
+			nla_strscpy(tmp, nla, sizeof(tmp));
+			val = tcp_ca_get_key_by_name(tmp, &ecn_ca);
+			if (val == TCP_CA_UNSPEC) {
+				NL_SET_ERR_MSG(extack, "Unknown tcp congestion algorithm");
+				return -EINVAL;
+			}
+		} else {
+			if (nla_len(nla) != sizeof(u32)) {
+				NL_SET_ERR_MSG_ATTR(extack, nla,
+						    "Invalid attribute in metrics");
+				return -EINVAL;
+			}
+			val = nla_get_u32(nla);
+		}
+		if (type == RTAX_ADVMSS && val > 65535 - 40)
+			val = 65535 - 40;
+		if (type == RTAX_MTU && val > 65535 - 15)
+			val = 65535 - 15;
+		if (type == RTAX_HOPLIMIT && val > 255)
+			val = 255;
+		if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK)) {
+			NL_SET_ERR_MSG(extack, "Unknown flag set in feature mask in metrics attribute");
+			return -EINVAL;
+		}
+		metrics[type - 1] = val;
+	}
+
+	if (ecn_ca)
+		metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA;
+
+	return 0;
+}
+
+struct dst_metrics *ip_fib_metrics_init(struct nlattr *fc_mx,
+					int fc_mx_len,
+					struct netlink_ext_ack *extack)
+{
+	struct dst_metrics *fib_metrics;
+	int err;
+
+	if (!fc_mx)
+		return (struct dst_metrics *)&dst_default_metrics;
+
+	fib_metrics = kzalloc_obj(*fib_metrics);
+	if (unlikely(!fib_metrics))
+		return ERR_PTR(-ENOMEM);
+
+	err = ip_metrics_convert(fc_mx, fc_mx_len, fib_metrics->metrics,
+				 extack);
+	if (!err) {
+		refcount_set(&fib_metrics->refcnt, 1);
+	} else {
+		kfree(fib_metrics);
+		fib_metrics = ERR_PTR(err);
+	}
+
+	return fib_metrics;
+}