x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 642 insertions, 0 deletions

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
new file mode 100644
index 000000000..2b94c2114
--- /dev/null
+++ b/net/sctp/sysctl.c
@@ -0,0 +1,642 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * (C) Copyright IBM Corp. 2002, 2004
+ * Copyright (c) 2002 Intel Corp.
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * Sysctl related interfaces for SCTP.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *    Mingqin Liu           <liuming@us.ibm.com>
+ *    Jon Grimm             <jgrimm@us.ibm.com>
+ *    Ardelle Fan           <ardelle.fan@intel.com>
+ *    Ryan Layer            <rmlayer@us.ibm.com>
+ *    Sridhar Samudrala     <sri@us.ibm.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <net/sctp/structs.h>
+#include <net/sctp/sctp.h>
+#include <linux/sysctl.h>
+
+static int timer_max = 86400000; /* ms in one day */
+static int sack_timer_min = 1;
+static int sack_timer_max = 500;
+static int addr_scope_max = SCTP_SCOPE_POLICY_MAX;
+static int rwnd_scale_max = 16;
+static int rto_alpha_min = 0;
+static int rto_beta_min = 0;
+static int rto_alpha_max = 1000;
+static int rto_beta_max = 1000;
+static int pf_expose_max = SCTP_PF_EXPOSE_MAX;
+static int ps_retrans_max = SCTP_PS_RETRANS_MAX;
+static int udp_port_max = 65535;
+
+static unsigned long max_autoclose_min = 0;
+static unsigned long max_autoclose_max =
+	(MAX_SCHEDULE_TIMEOUT / HZ > UINT_MAX)
+	? UINT_MAX : MAX_SCHEDULE_TIMEOUT / HZ;
+
+static int proc_sctp_do_hmac_alg(const struct ctl_table *ctl, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_rto_min(const struct ctl_table *ctl, int write,
+				void *buffer, size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_rto_max(const struct ctl_table *ctl, int write, void *buffer,
+				size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write, void *buffer,
+				 size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_alpha_beta(const struct ctl_table *ctl, int write,
+				   void *buffer, size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_auth(const struct ctl_table *ctl, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos);
+static int proc_sctp_do_probe_interval(const struct ctl_table *ctl, int write,
+				       void *buffer, size_t *lenp, loff_t *ppos);
+
+static struct ctl_table sctp_table[] = {
+	{
+		.procname	= "sctp_mem",
+		.data		= &sysctl_sctp_mem,
+		.maxlen		= sizeof(sysctl_sctp_mem),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax
+	},
+	{
+		.procname	= "sctp_rmem",
+		.data		= &sysctl_sctp_rmem,
+		.maxlen		= sizeof(sysctl_sctp_rmem),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "sctp_wmem",
+		.data		= &sysctl_sctp_wmem,
+		.maxlen		= sizeof(sysctl_sctp_wmem),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+};
+
+/* The following index defines are used in sctp_sysctl_net_register().
+ * If you add new items to the sctp_net_table, please ensure that
+ * the index values of these defines hold the same meaning indicated by
+ * their macro names when they appear in sctp_net_table.
+ */
+#define SCTP_RTO_MIN_IDX       0
+#define SCTP_RTO_MAX_IDX       1
+#define SCTP_PF_RETRANS_IDX    2
+#define SCTP_PS_RETRANS_IDX    3
+
+static const struct ctl_table sctp_net_table[] = {
+	[SCTP_RTO_MIN_IDX] = {
+		.procname	= "rto_min",
+		.data		= &init_net.sctp.rto_min,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_rto_min,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &init_net.sctp.rto_max
+	},
+	[SCTP_RTO_MAX_IDX] =  {
+		.procname	= "rto_max",
+		.data		= &init_net.sctp.rto_max,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_rto_max,
+		.extra1         = &init_net.sctp.rto_min,
+		.extra2         = &timer_max
+	},
+	[SCTP_PF_RETRANS_IDX] = {
+		.procname	= "pf_retrans",
+		.data		= &init_net.sctp.pf_retrans,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &init_net.sctp.ps_retrans,
+	},
+	[SCTP_PS_RETRANS_IDX] = {
+		.procname	= "ps_retrans",
+		.data		= &init_net.sctp.ps_retrans,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &init_net.sctp.pf_retrans,
+		.extra2		= &ps_retrans_max,
+	},
+	{
+		.procname	= "rto_initial",
+		.data		= &init_net.sctp.rto_initial,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &timer_max
+	},
+	{
+		.procname	= "rto_alpha_exp_divisor",
+		.data		= &init_net.sctp.rto_alpha,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_alpha_beta,
+		.extra1		= &rto_alpha_min,
+		.extra2		= &rto_alpha_max,
+	},
+	{
+		.procname	= "rto_beta_exp_divisor",
+		.data		= &init_net.sctp.rto_beta,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_alpha_beta,
+		.extra1		= &rto_beta_min,
+		.extra2		= &rto_beta_max,
+	},
+	{
+		.procname	= "max_burst",
+		.data		= &init_net.sctp.max_burst,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "cookie_preserve_enable",
+		.data		= &init_net.sctp.cookie_preserve_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "cookie_hmac_alg",
+		.data		= &init_net.sctp.cookie_auth_enable,
+		.maxlen		= 8,
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_hmac_alg,
+	},
+	{
+		.procname	= "valid_cookie_life",
+		.data		= &init_net.sctp.valid_cookie_life,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &timer_max
+	},
+	{
+		.procname	= "sack_timeout",
+		.data		= &init_net.sctp.sack_timeout,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = &sack_timer_min,
+		.extra2         = &sack_timer_max,
+	},
+	{
+		.procname	= "hb_interval",
+		.data		= &init_net.sctp.hb_interval,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &timer_max
+	},
+	{
+		.procname	= "association_max_retrans",
+		.data		= &init_net.sctp.max_retrans_association,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "path_max_retrans",
+		.data		= &init_net.sctp.max_retrans_path,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "max_init_retransmits",
+		.data		= &init_net.sctp.max_retrans_init,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "sndbuf_policy",
+		.data		= &init_net.sctp.sndbuf_policy,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "rcvbuf_policy",
+		.data		= &init_net.sctp.rcvbuf_policy,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "default_auto_asconf",
+		.data		= &init_net.sctp.default_auto_asconf,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "addip_enable",
+		.data		= &init_net.sctp.addip_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "addip_noauth_enable",
+		.data		= &init_net.sctp.addip_noauth,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "prsctp_enable",
+		.data		= &init_net.sctp.prsctp_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "reconf_enable",
+		.data		= &init_net.sctp.reconf_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "auth_enable",
+		.data		= &init_net.sctp.auth_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_auth,
+	},
+	{
+		.procname	= "intl_enable",
+		.data		= &init_net.sctp.intl_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "ecn_enable",
+		.data		= &init_net.sctp.ecn_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "plpmtud_probe_interval",
+		.data		= &init_net.sctp.probe_interval,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_probe_interval,
+	},
+	{
+		.procname	= "udp_port",
+		.data		= &init_net.sctp.udp_port,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_sctp_do_udp_port,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &udp_port_max,
+	},
+	{
+		.procname	= "encap_port",
+		.data		= &init_net.sctp.encap_port,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &udp_port_max,
+	},
+	{
+		.procname	= "addr_scope_policy",
+		.data		= &init_net.sctp.scope_policy,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &addr_scope_max,
+	},
+	{
+		.procname	= "rwnd_update_shift",
+		.data		= &init_net.sctp.rwnd_upd_shift,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= &rwnd_scale_max,
+	},
+	{
+		.procname	= "max_autoclose",
+		.data		= &init_net.sctp.max_autoclose,
+		.maxlen		= sizeof(unsigned long),
+		.mode		= 0644,
+		.proc_handler	= &proc_doulongvec_minmax,
+		.extra1		= &max_autoclose_min,
+		.extra2		= &max_autoclose_max,
+	},
+#ifdef CONFIG_NET_L3_MASTER_DEV
+	{
+		.procname	= "l3mdev_accept",
+		.data		= &init_net.sctp.l3mdev_accept,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+#endif
+	{
+		.procname	= "pf_enable",
+		.data		= &init_net.sctp.pf_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "pf_expose",
+		.data		= &init_net.sctp.pf_expose,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &pf_expose_max,
+	},
+};
+
+static int proc_sctp_do_hmac_alg(const struct ctl_table *ctl, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net,
+				       sctp.cookie_auth_enable);
+	struct ctl_table tbl;
+	char tmp[8] = {0};
+	int ret;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+
+	if (write) {
+		tbl.data = tmp;
+		tbl.maxlen = sizeof(tmp) - 1;
+		ret = proc_dostring(&tbl, 1, buffer, lenp, ppos);
+		if (ret)
+			return ret;
+		if (!strcmp(tmp, "sha256")) {
+			net->sctp.cookie_auth_enable = 1;
+			return 0;
+		}
+		if (!strcmp(tmp, "none")) {
+			net->sctp.cookie_auth_enable = 0;
+			return 0;
+		}
+		return -EINVAL;
+	}
+	if (net->sctp.cookie_auth_enable)
+		tbl.data = (char *)"sha256";
+	else
+		tbl.data = (char *)"none";
+	tbl.maxlen = strlen(tbl.data);
+	return proc_dostring(&tbl, 0, buffer, lenp, ppos);
+}
+
+static int proc_sctp_do_rto_min(const struct ctl_table *ctl, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net, sctp.rto_min);
+	unsigned int min = *(unsigned int *) ctl->extra1;
+	unsigned int max = *(unsigned int *) ctl->extra2;
+	struct ctl_table tbl;
+	int ret, new_value;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+	tbl.maxlen = sizeof(unsigned int);
+
+	if (write)
+		tbl.data = &new_value;
+	else
+		tbl.data = &net->sctp.rto_min;
+
+	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		if (new_value > max || new_value < min)
+			return -EINVAL;
+
+		net->sctp.rto_min = new_value;
+	}
+
+	return ret;
+}
+
+static int proc_sctp_do_rto_max(const struct ctl_table *ctl, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net, sctp.rto_max);
+	unsigned int min = *(unsigned int *) ctl->extra1;
+	unsigned int max = *(unsigned int *) ctl->extra2;
+	struct ctl_table tbl;
+	int ret, new_value;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+	tbl.maxlen = sizeof(unsigned int);
+
+	if (write)
+		tbl.data = &new_value;
+	else
+		tbl.data = &net->sctp.rto_max;
+
+	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		if (new_value > max || new_value < min)
+			return -EINVAL;
+
+		net->sctp.rto_max = new_value;
+	}
+
+	return ret;
+}
+
+static int proc_sctp_do_alpha_beta(const struct ctl_table *ctl, int write,
+				   void *buffer, size_t *lenp, loff_t *ppos)
+{
+	if (write)
+		pr_warn_once("Changing rto_alpha or rto_beta may lead to "
+			     "suboptimal rtt/srtt estimations!\n");
+
+	return proc_dointvec_minmax(ctl, write, buffer, lenp, ppos);
+}
+
+static int proc_sctp_do_auth(const struct ctl_table *ctl, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net, sctp.auth_enable);
+	struct ctl_table tbl;
+	int new_value, ret;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+	tbl.maxlen = sizeof(unsigned int);
+
+	if (write)
+		tbl.data = &new_value;
+	else
+		tbl.data = &net->sctp.auth_enable;
+
+	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		struct sock *sk = net->sctp.ctl_sock;
+
+		net->sctp.auth_enable = new_value;
+		/* Update the value in the control socket */
+		lock_sock(sk);
+		sctp_sk(sk)->ep->auth_enable = new_value;
+		release_sock(sk);
+	}
+
+	return ret;
+}
+
+static DEFINE_MUTEX(sctp_sysctl_mutex);
+
+static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net, sctp.udp_port);
+	unsigned int min = *(unsigned int *)ctl->extra1;
+	unsigned int max = *(unsigned int *)ctl->extra2;
+	struct ctl_table tbl;
+	int ret, new_value;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+	tbl.maxlen = sizeof(unsigned int);
+
+	if (write)
+		tbl.data = &new_value;
+	else
+		tbl.data = &net->sctp.udp_port;
+
+	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		struct sock *sk = net->sctp.ctl_sock;
+
+		if (new_value > max || new_value < min)
+			return -EINVAL;
+
+		mutex_lock(&sctp_sysctl_mutex);
+		net->sctp.udp_port = new_value;
+		sctp_udp_sock_stop(net);
+		if (new_value) {
+			ret = sctp_udp_sock_start(net);
+			if (ret)
+				net->sctp.udp_port = 0;
+		}
+
+		/* Update the value in the control socket */
+		lock_sock(sk);
+		sctp_sk(sk)->udp_port = htons(net->sctp.udp_port);
+		release_sock(sk);
+		mutex_unlock(&sctp_sysctl_mutex);
+	}
+
+	return ret;
+}
+
+static int proc_sctp_do_probe_interval(const struct ctl_table *ctl, int write,
+				       void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net = container_of(ctl->data, struct net,
+				       sctp.probe_interval);
+	struct ctl_table tbl;
+	int ret, new_value;
+
+	memset(&tbl, 0, sizeof(struct ctl_table));
+	tbl.maxlen = sizeof(unsigned int);
+
+	if (write)
+		tbl.data = &new_value;
+	else
+		tbl.data = &net->sctp.probe_interval;
+
+	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		if (new_value && new_value < SCTP_PROBE_TIMER_MIN)
+			return -EINVAL;
+
+		net->sctp.probe_interval = new_value;
+	}
+
+	return ret;
+}
+
+int sctp_sysctl_net_register(struct net *net)
+{
+	size_t table_size = ARRAY_SIZE(sctp_net_table);
+	struct ctl_table *table;
+	int i;
+
+	table = kmemdup(sctp_net_table, sizeof(sctp_net_table), GFP_KERNEL);
+	if (!table)
+		return -ENOMEM;
+
+	for (i = 0; i < table_size; i++)
+		table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp;
+
+	table[SCTP_RTO_MIN_IDX].extra2 = &net->sctp.rto_max;
+	table[SCTP_RTO_MAX_IDX].extra1 = &net->sctp.rto_min;
+	table[SCTP_PF_RETRANS_IDX].extra2 = &net->sctp.ps_retrans;
+	table[SCTP_PS_RETRANS_IDX].extra1 = &net->sctp.pf_retrans;
+
+	net->sctp.sysctl_header = register_net_sysctl_sz(net, "net/sctp",
+							 table, table_size);
+	if (net->sctp.sysctl_header == NULL) {
+		kfree(table);
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+void sctp_sysctl_net_unregister(struct net *net)
+{
+	struct ctl_table_header *header = net->sctp.sysctl_header;
+	const struct ctl_table *table;
+
+	if (!header)
+		return;
+
+	table = header->ctl_table_arg;
+	unregister_net_sysctl_table(header);
+	kfree(table);
+	net->sctp.sysctl_header = NULL;
+}
+
+static struct ctl_table_header *sctp_sysctl_header;
+
+/* Sysctl registration.  */
+void sctp_sysctl_register(void)
+{
+	sctp_sysctl_header = register_net_sysctl(&init_net, "net/sctp", sctp_table);
+}
+
+/* Sysctl deregistration.  */
+void sctp_sysctl_unregister(void)
+{
+	unregister_net_sysctl_table(sctp_sysctl_header);
+}