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, 186 insertions, 0 deletions

diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
new file mode 100644
index 000000000..c6de5ce79
--- /dev/null
+++ b/net/ipv4/tcp_highspeed.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sally Floyd's High Speed TCP (RFC 3649) congestion control
+ *
+ * See https://www.icir.org/floyd/hstcp.html
+ *
+ * John Heffner <jheffner@psc.edu>
+ */
+
+#include <linux/module.h>
+#include <net/tcp.h>
+
+/* From AIMD tables from RFC 3649 appendix B,
+ * with fixed-point MD scaled <<8.
+ */
+static const struct hstcp_aimd_val {
+	unsigned int cwnd;
+	unsigned int md;
+} hstcp_aimd_vals[] = {
+	{     38,  128, /*  0.50 */ },
+	{    118,  112, /*  0.44 */ },
+	{    221,  104, /*  0.41 */ },
+	{    347,   98, /*  0.38 */ },
+	{    495,   93, /*  0.37 */ },
+	{    663,   89, /*  0.35 */ },
+	{    851,   86, /*  0.34 */ },
+	{   1058,   83, /*  0.33 */ },
+	{   1284,   81, /*  0.32 */ },
+	{   1529,   78, /*  0.31 */ },
+	{   1793,   76, /*  0.30 */ },
+	{   2076,   74, /*  0.29 */ },
+	{   2378,   72, /*  0.28 */ },
+	{   2699,   71, /*  0.28 */ },
+	{   3039,   69, /*  0.27 */ },
+	{   3399,   68, /*  0.27 */ },
+	{   3778,   66, /*  0.26 */ },
+	{   4177,   65, /*  0.26 */ },
+	{   4596,   64, /*  0.25 */ },
+	{   5036,   62, /*  0.25 */ },
+	{   5497,   61, /*  0.24 */ },
+	{   5979,   60, /*  0.24 */ },
+	{   6483,   59, /*  0.23 */ },
+	{   7009,   58, /*  0.23 */ },
+	{   7558,   57, /*  0.22 */ },
+	{   8130,   56, /*  0.22 */ },
+	{   8726,   55, /*  0.22 */ },
+	{   9346,   54, /*  0.21 */ },
+	{   9991,   53, /*  0.21 */ },
+	{  10661,   52, /*  0.21 */ },
+	{  11358,   52, /*  0.20 */ },
+	{  12082,   51, /*  0.20 */ },
+	{  12834,   50, /*  0.20 */ },
+	{  13614,   49, /*  0.19 */ },
+	{  14424,   48, /*  0.19 */ },
+	{  15265,   48, /*  0.19 */ },
+	{  16137,   47, /*  0.19 */ },
+	{  17042,   46, /*  0.18 */ },
+	{  17981,   45, /*  0.18 */ },
+	{  18955,   45, /*  0.18 */ },
+	{  19965,   44, /*  0.17 */ },
+	{  21013,   43, /*  0.17 */ },
+	{  22101,   43, /*  0.17 */ },
+	{  23230,   42, /*  0.17 */ },
+	{  24402,   41, /*  0.16 */ },
+	{  25618,   41, /*  0.16 */ },
+	{  26881,   40, /*  0.16 */ },
+	{  28193,   39, /*  0.16 */ },
+	{  29557,   39, /*  0.15 */ },
+	{  30975,   38, /*  0.15 */ },
+	{  32450,   38, /*  0.15 */ },
+	{  33986,   37, /*  0.15 */ },
+	{  35586,   36, /*  0.14 */ },
+	{  37253,   36, /*  0.14 */ },
+	{  38992,   35, /*  0.14 */ },
+	{  40808,   35, /*  0.14 */ },
+	{  42707,   34, /*  0.13 */ },
+	{  44694,   33, /*  0.13 */ },
+	{  46776,   33, /*  0.13 */ },
+	{  48961,   32, /*  0.13 */ },
+	{  51258,   32, /*  0.13 */ },
+	{  53677,   31, /*  0.12 */ },
+	{  56230,   30, /*  0.12 */ },
+	{  58932,   30, /*  0.12 */ },
+	{  61799,   29, /*  0.12 */ },
+	{  64851,   28, /*  0.11 */ },
+	{  68113,   28, /*  0.11 */ },
+	{  71617,   27, /*  0.11 */ },
+	{  75401,   26, /*  0.10 */ },
+	{  79517,   26, /*  0.10 */ },
+	{  84035,   25, /*  0.10 */ },
+	{  89053,   24, /*  0.10 */ },
+};
+
+#define HSTCP_AIMD_MAX	ARRAY_SIZE(hstcp_aimd_vals)
+
+struct hstcp {
+	u32	ai;
+};
+
+static void hstcp_init(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct hstcp *ca = inet_csk_ca(sk);
+
+	ca->ai = 0;
+
+	/* Ensure the MD arithmetic works.  This is somewhat pedantic,
+	 * since I don't think we will see a cwnd this large. :) */
+	tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
+}
+
+static void hstcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct hstcp *ca = inet_csk_ca(sk);
+
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	if (tcp_in_slow_start(tp))
+		tcp_slow_start(tp, acked);
+	else {
+		/* Update AIMD parameters.
+		 *
+		 * We want to guarantee that:
+		 *     hstcp_aimd_vals[ca->ai-1].cwnd <
+		 *     snd_cwnd <=
+		 *     hstcp_aimd_vals[ca->ai].cwnd
+		 */
+		if (tcp_snd_cwnd(tp) > hstcp_aimd_vals[ca->ai].cwnd) {
+			while (tcp_snd_cwnd(tp) > hstcp_aimd_vals[ca->ai].cwnd &&
+			       ca->ai < HSTCP_AIMD_MAX - 1)
+				ca->ai++;
+		} else if (ca->ai && tcp_snd_cwnd(tp) <= hstcp_aimd_vals[ca->ai-1].cwnd) {
+			while (ca->ai && tcp_snd_cwnd(tp) <= hstcp_aimd_vals[ca->ai-1].cwnd)
+				ca->ai--;
+		}
+
+		/* Do additive increase */
+		if (tcp_snd_cwnd(tp) < tp->snd_cwnd_clamp) {
+			/* cwnd = cwnd + a(w) / cwnd */
+			tp->snd_cwnd_cnt += ca->ai + 1;
+			if (tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
+				tp->snd_cwnd_cnt -= tcp_snd_cwnd(tp);
+				tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
+			}
+		}
+	}
+}
+
+static u32 hstcp_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct hstcp *ca = inet_csk_ca(sk);
+
+	/* Do multiplicative decrease */
+	return max(tcp_snd_cwnd(tp) - ((tcp_snd_cwnd(tp) * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);
+}
+
+static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
+	.init		= hstcp_init,
+	.ssthresh	= hstcp_ssthresh,
+	.undo_cwnd	= tcp_reno_undo_cwnd,
+	.cong_avoid	= hstcp_cong_avoid,
+
+	.owner		= THIS_MODULE,
+	.name		= "highspeed"
+};
+
+static int __init hstcp_register(void)
+{
+	BUILD_BUG_ON(sizeof(struct hstcp) > ICSK_CA_PRIV_SIZE);
+	return tcp_register_congestion_control(&tcp_highspeed);
+}
+
+static void __exit hstcp_unregister(void)
+{
+	tcp_unregister_congestion_control(&tcp_highspeed);
+}
+
+module_init(hstcp_register);
+module_exit(hstcp_unregister);
+
+MODULE_AUTHOR("John Heffner");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("High Speed TCP");